diff --git a/.travis.yml b/.travis.yml
index 447d4fd..e1c8002 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -12,13 +12,16 @@ env:
 
 android:
   components:
-    - build-tools-19.1.0
+    - platform-tools
+    - tools
+    - build-tools-23.0.3
     - android-15
     - android-16
     - android-17
     - android-18
     - android-19
     - android-21
+    - android-23
     - sys-img-armeabi-v7a-android-15
     - sys-img-armeabi-v7a-android-16
     - sys-img-armeabi-v7a-android-17
diff --git a/ProviGenLib/build.gradle b/ProviGenLib/build.gradle
index 34867f5..7b9651a 100644
--- a/ProviGenLib/build.gradle
+++ b/ProviGenLib/build.gradle
@@ -9,4 +9,9 @@ sourceSets {
             srcDir 'src'
         }
     }
+}
+
+task generateSourcesJar(type: Jar) {
+    from sourceSets.main.java.srcDirs
+    classifier 'sources'
 }
\ No newline at end of file
diff --git a/ProviGenLib/src/com/tjeannin/provigen/ProviGenBaseContract.java b/ProviGenLib/src/com/tjeannin/provigen/ProviGenBaseContract.java
index 267aca9..deef5ee 100644
--- a/ProviGenLib/src/com/tjeannin/provigen/ProviGenBaseContract.java
+++ b/ProviGenLib/src/com/tjeannin/provigen/ProviGenBaseContract.java
@@ -13,8 +13,8 @@ public interface ProviGenBaseContract {
     /**
      * The unique ID for a row.
      */
-    @Id
+    @Id(autoincrement = true)
     @Column(Type.INTEGER)
-    public static final String _ID = BaseColumns._ID;
+    String _ID = BaseColumns._ID;
 
 }
diff --git a/ProviGenLib/src/com/tjeannin/provigen/ProviGenOpenHelper.java b/ProviGenLib/src/com/tjeannin/provigen/ProviGenOpenHelper.java
index 5214b6f..7e6db3f 100644
--- a/ProviGenLib/src/com/tjeannin/provigen/ProviGenOpenHelper.java
+++ b/ProviGenLib/src/com/tjeannin/provigen/ProviGenOpenHelper.java
@@ -42,9 +42,14 @@ public void onCreate(SQLiteDatabase database) {
 
     @Override
     public void onUpgrade(SQLiteDatabase database, int oldVersion, int newVersion) {
+        // create new tables if not exists
+        onCreate(database);
+
+        // add missing columns
         if (newVersion > oldVersion) {
-            for (Class contract : contracts)
+            for (Class contract : contracts) {
                 TableUpdater.addMissingColumns(database, contract);
+            }
         }
     }
 }
diff --git a/ProviGenLib/src/com/tjeannin/provigen/ProviGenProvider.java b/ProviGenLib/src/com/tjeannin/provigen/ProviGenProvider.java
index 975019c..379dca8 100644
--- a/ProviGenLib/src/com/tjeannin/provigen/ProviGenProvider.java
+++ b/ProviGenLib/src/com/tjeannin/provigen/ProviGenProvider.java
@@ -4,27 +4,36 @@
 import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;
 import android.database.sqlite.SQLiteOpenHelper;
+import android.database.sqlite.SQLiteQueryBuilder;
 import android.net.Uri;
+import android.os.Build;
 import android.text.TextUtils;
+import com.tjeannin.provigen.helper.ContractUtil;
 import com.tjeannin.provigen.model.Contract;
 
 import java.util.ArrayList;
+import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Map;
 
 /**
  * Behaves as a {@link ContentProvider} for the given contract class.
  */
 public abstract class ProviGenProvider extends ContentProvider {
 
-    private List<Contract> contracts = new ArrayList<Contract>();
-
-    private UriMatcher uriMatcher;
     private static final int ITEM = 1;
     private static final int ITEM_ID = 2;
-    private SQLiteOpenHelper openHelper;
+    private static final int INNER_JOIN = 3;
+    private static final int LEFT_OUTER_JOIN = 4;
+    private static final int CROSS_JOIN = 5;
+
+    private List<Contract> contracts = new ArrayList<>();
+    private UriMatcher uriMatcher;
+    private SQLiteOpenHelper[] openHelpers;
 
     /**
      * This method should return an instance of a {@link android.database.sqlite.SQLiteOpenHelper}.
+     * If you want to use multiple databases override {@link #openHelpers(Context)} and you may return null in this method.
      * It will be called only once, so you can safely create a new instance of the SQLiteOpenHelper on the method body.
      *
      * @param context A context to pass to the SQLiteOpenHelper instance while creating it.
@@ -32,6 +41,15 @@ public abstract class ProviGenProvider extends ContentProvider {
      */
     public abstract SQLiteOpenHelper openHelper(Context context);
 
+    /**
+     * Override if you want to use multiple databases.
+     * @param context A context to pass to the SQLiteOpenHelper instance while creating it.
+     * @return the SQLiteOpenHelper[] that the ProviGenProvider will use.
+     */
+    public SQLiteOpenHelper [] openHelpers(Context context) {
+        return new SQLiteOpenHelper[] { openHelper(context) };
+    }
+
     /**
      * This method should return the list of contract classes that the ProviGenProvider will use.
      * It will be called only once.
@@ -40,154 +58,302 @@ public abstract class ProviGenProvider extends ContentProvider {
      */
     public abstract Class[] contractClasses();
 
+    /**
+     * Override if you want to use multiple databases.
+     * This method should return the array of array contract classes that the ProviGenProvider will use.
+     * It will be called only once.
+     *
+     * @return an array of array of contract classes.
+     */
+    public Class[][] contractClassesMultipleDb() {
+        return new Class[][] { contractClasses() };
+    }
+
+    /**
+     * Override for insert conflict resolver. By default return SQLiteDatabase.CONFLICT_NONE.
+     */
+    public int conflictAlgorithm() {
+        return SQLiteDatabase.CONFLICT_NONE;
+    }
+
+    /**
+     * Whether to call the getContentResolver().notifyChange(uri, null) method after insert.
+     * @return true or false
+     */
+    public boolean insertNotifyChange() {
+        return true;
+    }
+
+    /**
+     * Whether to call the getContentResolver().notifyChange(uri, null) method after update.
+     * @return true or false
+     */
+    public boolean updateNotifyChange() {
+        return true;
+    }
+
+    /**
+     * Whether to call the getContentResolver().notifyChange(uri, null) method after delete.
+     * @return true or false
+     */
+    public boolean deleteNotifyChange() {
+        return true;
+    }
+
+    /**
+     * Get max number of join entities (by default 10)
+     * @return Max number of join entities
+     */
+    public int maxJoinEntities() {
+        return 10;
+    }
+
     @Override
     public boolean onCreate() {
+        openHelpers = openHelpers(getContext());
 
-        openHelper = openHelper(getContext());
-        for (Class contract : contractClasses()) {
-            contracts.add(new Contract(contract));
+        for(Class[] contractArray : contractClassesMultipleDb()) {
+            for (Class contract : contractArray) {
+                contracts.add(new Contract(contract));
+            }
         }
 
         uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
         for (Contract contract : contracts) {
-            uriMatcher.addURI(contract.getAuthority(), contract.getTable(), ITEM);
-            uriMatcher.addURI(contract.getAuthority(), contract.getTable() + "/#", ITEM_ID);
+            StringBuilder innerJoinPathSegment;
+            StringBuilder leftOuterJoinPathSegment;
+            StringBuilder crossJoinPathSegment;
+
+            if(contract.getDbName() == null) {
+                uriMatcher.addURI(contract.getAuthority(), contract.getTable(), ITEM);
+                uriMatcher.addURI(contract.getAuthority(), contract.getTable() + "/#", ITEM_ID);
+
+                innerJoinPathSegment = new StringBuilder(contract.getTable()).append("/inner_join/*/*");
+                leftOuterJoinPathSegment = new StringBuilder(contract.getTable()).append("/left_outer_join/*/*");
+                crossJoinPathSegment = new StringBuilder(contract.getTable()).append("/cross_join/*/*");
+            } else {
+                uriMatcher.addURI(contract.getAuthority(), contract.getDbName() + "/" + contract.getTable(), ITEM);
+                uriMatcher.addURI(contract.getAuthority(), contract.getDbName() + "/" + contract.getTable() + "/#", ITEM_ID);
+
+                innerJoinPathSegment = new StringBuilder(contract.getDbName()).append("/").append(contract.getTable()).append("/inner_join/*/*");
+                leftOuterJoinPathSegment = new StringBuilder(contract.getDbName()).append("/").append(contract.getTable()).append("/left_outer_join/*/*");
+                crossJoinPathSegment = new StringBuilder(contract.getDbName()).append("/").append(contract.getTable()).append("/cross_join/*/*");
+            }
+
+            for(int i = 0; i < maxJoinEntities(); i++) {
+                uriMatcher.addURI(contract.getAuthority(), innerJoinPathSegment.toString(), INNER_JOIN);
+                uriMatcher.addURI(contract.getAuthority(), leftOuterJoinPathSegment.toString(), LEFT_OUTER_JOIN);
+                uriMatcher.addURI(contract.getAuthority(), crossJoinPathSegment.toString(), CROSS_JOIN);
+                innerJoinPathSegment.append("/*/*");
+                leftOuterJoinPathSegment.append("/*/*");
+                crossJoinPathSegment.append("/*/*");
+            }
         }
 
         return true;
     }
 
     @Override
-    public int delete(Uri uri, String selection, String[] selectionArgs) {
-        SQLiteDatabase database = openHelper.getWritableDatabase();
-
-        int numberOfRowsAffected = 0;
+    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
+        SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
         Contract contract = findMatchingContract(uri);
+        SQLiteDatabase db = openDatabase(contract, true);
+        Cursor cursor;
 
         switch (uriMatcher.match(uri)) {
             case ITEM:
-                numberOfRowsAffected = database.delete(contract.getTable(), selection, selectionArgs);
+                queryBuilder.setTables(contract.getTable());
+                cursor = queryBuilder.query(db, projection, selection, selectionArgs, null, null, sortOrder);
                 break;
+
             case ITEM_ID:
                 String itemId = String.valueOf(ContentUris.parseId(uri));
-
                 if (TextUtils.isEmpty(selection)) {
-                    numberOfRowsAffected = database.delete(contract.getTable(), contract.getIdField() + " = ? ", new String[]{itemId});
+                    queryBuilder.setTables(contract.getTable());
+                    cursor = queryBuilder.query(db, projection, contract.getIdFields().get(0) + " = ? ", new String[]{itemId}, null, null, sortOrder);
                 } else {
-                    numberOfRowsAffected = database.delete(contract.getTable(), selection + " AND " +
-                            contract.getIdField() + " = ? ", appendToStringArray(selectionArgs, itemId));
+                    queryBuilder.setTables(contract.getTable());
+                    cursor = queryBuilder.query(db, projection, selection + " AND " + contract.getIdFields().get(0) + " = ? ", appendToStringArray(selectionArgs, itemId), null, null, sortOrder);
                 }
                 break;
+
+            // JOINs
+            case INNER_JOIN:
+            case LEFT_OUTER_JOIN:
+            case CROSS_JOIN:
+                Map<String, String> joinProjectionMap = new LinkedHashMap<>();
+                for(String field : projection) {
+                    joinProjectionMap.put(field, field.contains(".") ? field + " AS " + ContractUtil.joinName(field.substring(0, field.indexOf(".")), field.substring(field.indexOf(".") + 1)) : field);
+                }
+                queryBuilder.setProjectionMap(joinProjectionMap);
+                queryBuilder.setTables(parseJoinUri(uri, contract.getDbName() != null));
+                cursor = queryBuilder.query(db, projection, selection, selectionArgs, null, null, sortOrder);
+                break;
+
             default:
                 throw new IllegalArgumentException("Unknown uri " + uri);
         }
 
-        if (numberOfRowsAffected > 0) {
-            getContext().getContentResolver().notifyChange(uri, null);
-        }
-        return numberOfRowsAffected;
+        // Make sure that potential listeners are getting notified.
+        cursor.setNotificationUri(getContext().getContentResolver(), uri);
+
+        return cursor;
     }
 
     @Override
-    public String getType(Uri uri) {
-
+    public Uri insert(Uri uri, ContentValues values) {
         Contract contract = findMatchingContract(uri);
+        SQLiteDatabase db = openDatabase(contract, false);
 
         switch (uriMatcher.match(uri)) {
             case ITEM:
-                return "vnd.android.cursor.dir/vdn." + contract.getTable();
-            case ITEM_ID:
-                return "vnd.android.cursor.item/vdn." + contract.getTable();
+                long rowId;
+                if(conflictAlgorithm() == SQLiteDatabase.CONFLICT_NONE) {
+                    rowId = db.insert(contract.getTable(), null, values);
+                } else {
+                    rowId = db.insertWithOnConflict(contract.getTable(), null, values, conflictAlgorithm());
+                }
+
+                Uri rowUri = Uri.EMPTY;
+                if (rowId > 0) {
+                    rowUri = ContentUris.withAppendedId(uri, rowId);
+                }
+                if(insertNotifyChange()) {
+                    getContext().getContentResolver().notifyChange(uri, null);
+                }
+                return rowUri;
+
             default:
                 throw new IllegalArgumentException("Unknown uri " + uri);
         }
     }
 
     @Override
-    public Uri insert(Uri uri, ContentValues values) {
-        SQLiteDatabase database = openHelper.getWritableDatabase();
-
+    public int bulkInsert(Uri uri, ContentValues[] values) {
         Contract contract = findMatchingContract(uri);
+        SQLiteDatabase db = openDatabase(contract, false);
+
         switch (uriMatcher.match(uri)) {
             case ITEM:
-                long itemId = database.insert(contract.getTable(), null, values);
-                getContext().getContentResolver().notifyChange(uri, null);
-                return Uri.withAppendedPath(uri, String.valueOf(itemId));
+                db.beginTransaction();
+                try {
+                    for (ContentValues cv : values) {
+                        if(conflictAlgorithm() == SQLiteDatabase.CONFLICT_NONE) {
+                            db.insert(contract.getTable(), null, cv);
+                        } else {
+                            db.insertWithOnConflict(contract.getTable(), null, cv, conflictAlgorithm());
+                        }
+                    }
+                    db.setTransactionSuccessful();
+
+                    if(insertNotifyChange()) {
+                        getContext().getContentResolver().notifyChange(uri, null);
+                    }
+                } finally {
+                    db.endTransaction();
+                }
+                return values.length;
+
             default:
                 throw new IllegalArgumentException("Unknown uri " + uri);
         }
     }
 
     @Override
-    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
-        SQLiteDatabase database = openHelper.getReadableDatabase();
-
+    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
         Contract contract = findMatchingContract(uri);
-        Cursor cursor = null;
+        SQLiteDatabase db = openDatabase(contract, false);
+        int numberOfRowsAffected;
 
         switch (uriMatcher.match(uri)) {
             case ITEM:
-                cursor = database.query(contract.getTable(), projection, selection, selectionArgs, "", "", sortOrder);
+                numberOfRowsAffected = db.update(contract.getTable(), values, selection, selectionArgs);
                 break;
+
             case ITEM_ID:
                 String itemId = String.valueOf(ContentUris.parseId(uri));
                 if (TextUtils.isEmpty(selection)) {
-                    cursor = database.query(contract.getTable(), projection, contract.getIdField() + " = ? ", new String[]{itemId}, "", "", sortOrder);
+                    numberOfRowsAffected = db.update(contract.getTable(), values, contract.getIdFields().get(0) + " = ? ", new String[]{itemId});
                 } else {
-                    cursor = database.query(contract.getTable(), projection, selection + " AND " + contract.getIdField() + " = ? ",
-                            appendToStringArray(selectionArgs, itemId), "", "", sortOrder);
+                    numberOfRowsAffected = db.update(contract.getTable(), values, selection + " AND " + contract.getIdFields().get(0) + " = ? ",
+                            appendToStringArray(selectionArgs, itemId));
                 }
                 break;
+
             default:
                 throw new IllegalArgumentException("Unknown uri " + uri);
         }
-
-        // Make sure that potential listeners are getting notified.
-        cursor.setNotificationUri(getContext().getContentResolver(), uri);
-
-        return cursor;
+        if(updateNotifyChange()) {
+            getContext().getContentResolver().notifyChange(uri, null);
+        }
+        return numberOfRowsAffected;
     }
 
     @Override
-    public int update(Uri uri, ContentValues values, String selection,
-                      String[] selectionArgs) {
-        SQLiteDatabase database = openHelper.getWritableDatabase();
-
+    public int delete(Uri uri, String selection, String[] selectionArgs) {
         Contract contract = findMatchingContract(uri);
-        int numberOfRowsAffected = 0;
+        SQLiteDatabase db = openDatabase(contract, false);
+        int numberOfRowsAffected;
 
         switch (uriMatcher.match(uri)) {
             case ITEM:
-                numberOfRowsAffected = database.update(contract.getTable(), values, selection, selectionArgs);
+            case INNER_JOIN:
+            case LEFT_OUTER_JOIN:
+            case CROSS_JOIN:
+                numberOfRowsAffected = db.delete(contract.getTable(), selection, selectionArgs);
                 break;
+
             case ITEM_ID:
                 String itemId = String.valueOf(ContentUris.parseId(uri));
-
                 if (TextUtils.isEmpty(selection)) {
-                    numberOfRowsAffected = database.update(contract.getTable(), values, contract.getIdField() + " = ? ", new String[]{itemId});
+                    numberOfRowsAffected = db.delete(contract.getTable(), contract.getIdFields().get(0) + " = ? ", new String[]{itemId});
                 } else {
-                    numberOfRowsAffected = database.update(contract.getTable(), values, selection + " AND " + contract.getIdField() + " = ? ",
-                            appendToStringArray(selectionArgs, itemId));
+                    numberOfRowsAffected = db.delete(contract.getTable(), selection + " AND " +
+                            contract.getIdFields().get(0) + " = ? ", appendToStringArray(selectionArgs, itemId));
                 }
                 break;
+
             default:
                 throw new IllegalArgumentException("Unknown uri " + uri);
         }
-
-        if (numberOfRowsAffected > 0) {
+        if(deleteNotifyChange()) {
             getContext().getContentResolver().notifyChange(uri, null);
         }
         return numberOfRowsAffected;
     }
 
+    @Override
+    public String getType(Uri uri) {
+        Contract contract = findMatchingContract(uri);
+        switch (uriMatcher.match(uri)) {
+            case ITEM:
+            case INNER_JOIN:
+            case LEFT_OUTER_JOIN:
+            case CROSS_JOIN:
+                return "vnd.android.cursor.dir/vdn." + contract.getAuthority() + '.' + contract.getTable();
+
+            case ITEM_ID:
+                return "vnd.android.cursor.item/vdn."  + contract.getAuthority() + '.' + contract.getTable();
+
+            default:
+                throw new IllegalArgumentException("Unknown uri " + uri);
+        }
+    }
+
     /**
      * @param uri The {@link Uri} to be matched.
      * @return A {@link com.tjeannin.provigen.model.Contract} matching the given {@link Uri}.
      */
     public Contract findMatchingContract(Uri uri) {
         for (Contract contract : contracts) {
-            if (contract.getTable().equals(uri.getPathSegments().get(0))) {
-                return contract;
+            if(contract.getDbName() == null) {
+                if (contract.getTable().equals(uri.getPathSegments().get(0))) {
+                    return contract;
+                }
+            } else {
+                if (contract.getDbName().equals(uri.getPathSegments().get(0)) && contract.getTable().equals(uri.getPathSegments().get(1))) {
+                    return contract;
+                }
             }
         }
         return null;
@@ -211,4 +377,76 @@ private static String[] appendToStringArray(String[] array, String element) {
         }
     }
 
+    /**
+     * Open database
+     * @param contract Contract class
+     * @param readOnly Open database only for read
+     * @return SQLiteDatabase object
+     */
+    private SQLiteDatabase openDatabase(Contract contract, boolean readOnly) {
+        if(contract.getDbName() == null) {
+            return readOnly ? openHelpers[0].getReadableDatabase() : openHelpers[0].getWritableDatabase();
+        }
+        else {
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
+                for (SQLiteOpenHelper helper : openHelpers) {
+                    if (contract.getDbName().equals(helper.getDatabaseName())) {
+                        return readOnly ? helper.getReadableDatabase() : helper.getWritableDatabase();
+                    }
+                }
+            }
+            return readOnly ? openHelpers[1].getReadableDatabase() : openHelpers[1].getWritableDatabase();
+        }
+    }
+
+    /**
+     * Return join expression as string from URI
+     * @param uri Join URI
+     * @param hasDbName True if URI has database name
+     * @return Join expression
+     */
+    private String parseJoinUri(Uri uri, boolean hasDbName) {
+        List<String> pathSegments = uri.getPathSegments();
+        if(pathSegments.size() > 3) {
+            StringBuilder builder = new StringBuilder();
+            String table1 = pathSegments.get(hasDbName ? 1 : 0);
+            String joinType;
+            switch (pathSegments.get(hasDbName ? 2 : 1)) {
+                case "inner_join":
+                    joinType = " INNER JOIN ";
+                    break;
+
+                case "left_outer_join":
+                    joinType = " LEFT OUTER JOIN ";
+                    break;
+
+                case "cross_join":
+                    joinType = " CROSS JOIN ";
+                    break;
+
+                default:
+                    joinType = "";
+            }
+            builder.append(table1);
+
+            List<String> subList = pathSegments.subList(hasDbName ? 3 : 2, pathSegments.size()); // ex: {"doctor", "doctor_id:id", ...}
+            for(String tableOrFields : subList) {
+                // fields separate by ":"
+                if(tableOrFields.contains(":")) {
+                    builder.append(" ON ")
+                            .append(tableOrFields.substring(0, tableOrFields.indexOf(":")))
+                            .append(" = ")
+                            .append(tableOrFields.substring(tableOrFields.indexOf(":") + 1));
+                }
+                // table name
+                else {
+                    builder.append(joinType).append(" ").append(tableOrFields);
+                }
+            }
+
+            return builder.toString();
+        } else {
+            throw new IllegalArgumentException("Illegal join URI: " + uri);
+        }
+    }
 }
diff --git a/ProviGenLib/src/com/tjeannin/provigen/annotation/ForeignKey.java b/ProviGenLib/src/com/tjeannin/provigen/annotation/ForeignKey.java
new file mode 100644
index 0000000..2d512b5
--- /dev/null
+++ b/ProviGenLib/src/com/tjeannin/provigen/annotation/ForeignKey.java
@@ -0,0 +1,19 @@
+package com.tjeannin.provigen.annotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Identifies a field of a contract class that should be used as a foreign key in the database. <br/>
+ * This annotation should be used alongside with a {@link Column} annotation.<br/><br/>
+ * <b>table</b> - The name of the table on which the foreign key is referenced.<br/>
+ * <b>column</b> - The name of the column on which the foreign key is referenced.<br/>
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.FIELD)
+public @interface ForeignKey {
+    String table();
+    String column();
+}
diff --git a/ProviGenLib/src/com/tjeannin/provigen/annotation/Id.java b/ProviGenLib/src/com/tjeannin/provigen/annotation/Id.java
index c2326de..11e5234 100644
--- a/ProviGenLib/src/com/tjeannin/provigen/annotation/Id.java
+++ b/ProviGenLib/src/com/tjeannin/provigen/annotation/Id.java
@@ -7,9 +7,10 @@
 
 /**
  * Identifies a field of a contract class that should be used as a primary key in the database. <br/>
- * This annotation should be used alongside with a {@link Column} annotation.
+ * This annotation should be used alongside with a {@link Column} annotation. The autoincrement attribute should be true or false (by default).
  */
 @Retention(RetentionPolicy.RUNTIME)
 @Target(ElementType.FIELD)
 public @interface Id {
+    boolean autoincrement() default false;
 }
diff --git a/ProviGenLib/src/com/tjeannin/provigen/helper/ContractUtil.java b/ProviGenLib/src/com/tjeannin/provigen/helper/ContractUtil.java
new file mode 100644
index 0000000..82e4b0a
--- /dev/null
+++ b/ProviGenLib/src/com/tjeannin/provigen/helper/ContractUtil.java
@@ -0,0 +1,37 @@
+package com.tjeannin.provigen.helper;
+
+/**
+ * Created by Dre on 08.04.2016.
+ *
+ */
+public class ContractUtil {
+
+    /**
+     * Return full name of field
+     * @param table Table
+     * @param field Field
+     * @return Full name of field
+     */
+    public static String fullName(String table, String field) {
+        return table + "." + field;
+    }
+
+    /**
+     * Return name of field after join
+     * @param table Table
+     * @param field Field
+     * @return Name of field after join
+     */
+    public static String joinName(String table, String field) {
+        if(table.endsWith("_") && field.startsWith("_")) {
+            return table + field.substring(1 , field.length());
+        }
+        else if(table.endsWith("_") || field.startsWith("_")) {
+            return table + field;
+        }
+        else {
+            return table + "_" + field;
+        }
+    }
+
+}
diff --git a/ProviGenLib/src/com/tjeannin/provigen/helper/ProviGenUriBuilder.java b/ProviGenLib/src/com/tjeannin/provigen/helper/ProviGenUriBuilder.java
new file mode 100644
index 0000000..954259c
--- /dev/null
+++ b/ProviGenLib/src/com/tjeannin/provigen/helper/ProviGenUriBuilder.java
@@ -0,0 +1,88 @@
+package com.tjeannin.provigen.helper;
+
+import android.net.Uri;
+
+import com.tjeannin.provigen.model.JoinEntity;
+
+/**
+ * Created by Dre on 07.04.2016.
+ *
+ */
+public class ProviGenUriBuilder {
+
+    public enum JoinType {
+        INNER_JOIN, LEFT_OUTER_JOIN, CROSS_JOIN
+    }
+
+    /**
+     * Create content URI for contract class
+     * @param authority authority
+     * @param tableName tableName
+     * @return Content URI
+     */
+    public static Uri contentUri(String authority, String tableName) {
+        return contentUri(authority, tableName, null);
+    }
+
+    /**
+     * Create content URI with database name for contract class
+     * @param authority authority
+     * @param tableName tableName
+     * @param dbName database name
+     * @return Content URI
+     */
+    public static Uri contentUri(String authority, String tableName, String dbName) {
+        return Uri.parse("content://" + authority + "/" + (dbName != null ? dbName + "/" : "") + tableName);
+    }
+
+    /**
+     * Create URI for [inner, left outer, cross] join query
+     *
+     * @param joinType Type of join - INNER_JOIN, LEFT_OUTER_JOIN or CROSS_JOIN
+     * @param uriTable1 URI of left table
+     * @param joinEntities List of join entities (right table)
+     * @return URI
+     */
+    public static Uri joinUri(JoinType joinType, Uri uriTable1, JoinEntity ... joinEntities) {
+        if(joinEntities.length == 0) {
+            throw new IllegalArgumentException("joinEntities is empty");
+        }
+
+        boolean isCrossJoin = false;
+        String joinPath;
+        switch (joinType) {
+            case INNER_JOIN:
+                joinPath = "inner_join/";
+                break;
+
+            case LEFT_OUTER_JOIN:
+                joinPath = "left_outer_join/";
+                break;
+
+            case CROSS_JOIN:
+                joinPath = "cross_join/";
+                isCrossJoin = true;
+                break;
+
+            default:
+                joinPath = null;
+                break;
+        }
+
+        Uri joinUri = Uri.withAppendedPath(uriTable1, joinPath);
+        for(int i = 0; i < joinEntities.length; i++) {
+            String pathSegment;
+            if(isCrossJoin) {
+                pathSegment = joinEntities[i].getTableName();
+            } else {
+                pathSegment = joinEntities[i].getTableName() + "/" + joinEntities[i].getLeftField() + ":" + joinEntities[i].getRightField();
+            }
+            if(i < joinEntities.length - 1) {
+                pathSegment += "/";
+            }
+            joinUri = Uri.withAppendedPath(joinUri, pathSegment);
+        }
+
+        return joinUri;
+    }
+}
diff --git a/ProviGenLib/src/com/tjeannin/provigen/helper/TableBuilder.java b/ProviGenLib/src/com/tjeannin/provigen/helper/TableBuilder.java
index 7677c30..d2661e5 100644
--- a/ProviGenLib/src/com/tjeannin/provigen/helper/TableBuilder.java
+++ b/ProviGenLib/src/com/tjeannin/provigen/helper/TableBuilder.java
@@ -1,9 +1,12 @@
 package com.tjeannin.provigen.helper;
 
 import android.database.sqlite.SQLiteDatabase;
+
+import com.tjeannin.provigen.annotation.Column;
 import com.tjeannin.provigen.model.Constraint;
 import com.tjeannin.provigen.model.Contract;
 import com.tjeannin.provigen.model.ContractField;
+import com.tjeannin.provigen.model.ForeignKeyConstraint;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -21,7 +24,7 @@ public class TableBuilder {
      */
     public TableBuilder(Class contractClass) {
         contract = new Contract(contractClass);
-        constraints = new ArrayList<Constraint>();
+        constraints = new ArrayList<>();
     }
 
     /**
@@ -55,23 +58,62 @@ public TableBuilder addConstraint(String columnName, String constraintType, Stri
      */
     public String getSQL() {
 
-        StringBuilder builder = new StringBuilder("CREATE TABLE ");
+        StringBuilder builder = new StringBuilder("CREATE TABLE IF NOT EXISTS ");
         builder.append(contract.getTable()).append(" ( ");
 
         for (ContractField field : contract.getFields()) {
             builder.append(" ").append(field.name).append(" ").append(field.type);
-            if (field.name.equals(contract.getIdField())) {
-                builder.append(" PRIMARY KEY AUTOINCREMENT ");
+
+            boolean isSinglePrimaryKey = false;
+            // single PRIMARY KEY
+            if(contract.getIdFields().size() == 1) {
+                if (field.name.equals(contract.getIdFields().get(0))) {
+                    isSinglePrimaryKey = true;
+                    builder.append(" NOT NULL PRIMARY KEY ");
+
+                    if (field.type.equals(Column.Type.INTEGER)) {
+                        if(contract.isAutoincrement(field.name)) {
+                            builder.append(" AUTOINCREMENT "); // 123 456 789
+                        }
+                    }
+                }
             }
-            for (Constraint constraint : constraints) {
-                if (constraint.targetColumn.equals(field.name)) {
-                    builder.append(" ").append(constraint.type).append(" ON CONFLICT ").append(constraint.conflictClause);
+
+            if(!isSinglePrimaryKey) {
+                for (Constraint constraint : constraints) {
+                    if (constraint.targetColumn.equals(field.name)) {
+                        builder.append(" ").append(constraint.type).append(" ON CONFLICT ").append(constraint.conflictClause);
+                    }
                 }
             }
+
             builder.append(", ");
         }
-        builder.deleteCharAt(builder.length() - 2);
-        builder.append(" ) ");
+
+        // foreign keys
+        for(ForeignKeyConstraint foreignKey : contract.getForeignKeys()) {
+            builder.append("FOREIGN KEY (").append(foreignKey.getColumn()).append(") references ")
+                    .append(foreignKey.getTableReferenced()).append("(").append(foreignKey.getColumnReferenced()).append("), ");
+        }
+
+        // composite primary key
+        if(contract.getIdFields().size() > 1) {
+            builder.append("PRIMARY KEY (");
+            // пробегаем по полям, помеченными как @Id
+            for(int i = 0; i < contract.getIdFields().size(); i++) {
+                builder.append(contract.getIdFields().get(i));
+                if(i < contract.getIdFields().size() - 1) {
+                    builder.append(", ");
+                }
+            }
+            builder.append(")");
+        }
+        else {
+            // delete ',' in the end
+            builder.deleteCharAt(builder.length() - 2);
+        }
+        builder.append(")");
+
         return builder.toString();
     }
 
@@ -83,4 +125,4 @@ public String getSQL() {
     public void createTable(SQLiteDatabase database) {
         database.execSQL(getSQL());
     }
-}
+}
\ No newline at end of file
diff --git a/ProviGenLib/src/com/tjeannin/provigen/model/Contract.java b/ProviGenLib/src/com/tjeannin/provigen/model/Contract.java
index 44e6d98..7137ad7 100644
--- a/ProviGenLib/src/com/tjeannin/provigen/model/Contract.java
+++ b/ProviGenLib/src/com/tjeannin/provigen/model/Contract.java
@@ -3,23 +3,30 @@
 import android.net.Uri;
 import com.tjeannin.provigen.annotation.Column;
 import com.tjeannin.provigen.annotation.ContentUri;
+import com.tjeannin.provigen.annotation.ForeignKey;
 import com.tjeannin.provigen.annotation.Id;
 
 import java.lang.reflect.Field;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 public class Contract {
 
     private String authority;
-    private String idField;
+    private String dbName;
     private String tableName;
     private List<ContractField> contractFields;
+    private Map<String, Boolean> idFieldMap;
+    private List<ForeignKeyConstraint> foreignKeys;
 
     @SuppressWarnings({"rawtypes", "unchecked"})
     public Contract(Class contractClass) {
 
-        contractFields = new ArrayList<ContractField>();
+        idFieldMap = new HashMap<>();
+        contractFields = new ArrayList<>();
+        foreignKeys = new ArrayList<>();
 
         Field[] fields = contractClass.getFields();
         for (Field field : fields) {
@@ -30,6 +37,12 @@ public Contract(Class contractClass) {
                     Uri uri = (Uri) field.get(null);
                     authority = uri.getAuthority();
                     tableName = uri.getLastPathSegment();
+
+                    List<String> pathSegments = uri.getPathSegments();
+                    if(pathSegments.size() == 2) {
+                        dbName = pathSegments.get(0);
+                    }
+
                 } catch (Exception e) {
                     e.printStackTrace();
                 }
@@ -38,7 +51,23 @@ public Contract(Class contractClass) {
             Id id = field.getAnnotation(Id.class);
             if (id != null) {
                 try {
-                    idField = (String) field.get(null);
+                    String idField = (String) field.get(null);
+                    idFieldMap.put(idField, id.autoincrement());
+                } catch (Exception e) {
+                    e.printStackTrace();
+                }
+            }
+
+            ForeignKey foreignKey = field.getAnnotation(ForeignKey.class);
+            if(foreignKey != null) {
+                try {
+                    ForeignKeyConstraint foreignKeyConstraint = null;
+                    if(foreignKey.table() != null && foreignKey.column() != null) {
+                        foreignKeyConstraint = new ForeignKeyConstraint((String) field.get(null), foreignKey.table(), foreignKey.column());
+                    }
+                    if(foreignKeyConstraint != null) {
+                        foreignKeys.add(foreignKeyConstraint);
+                    }
                 } catch (Exception e) {
                     e.printStackTrace();
                 }
@@ -59,15 +88,27 @@ public String getAuthority() {
         return authority;
     }
 
-    public String getIdField() {
-        return idField;
-    }
-
     public String getTable() {
         return tableName;
     }
 
+    public String getDbName() {
+        return dbName;
+    }
+
+    public List<String> getIdFields() {
+        return new ArrayList<>(idFieldMap.keySet());
+    }
+
     public List<ContractField> getFields() {
         return contractFields;
     }
+
+    public boolean isAutoincrement(String field) {
+        return idFieldMap.get(field);
+    }
+
+    public List<ForeignKeyConstraint> getForeignKeys() {
+        return foreignKeys;
+    }
 }
diff --git a/ProviGenLib/src/com/tjeannin/provigen/model/ForeignKeyConstraint.java b/ProviGenLib/src/com/tjeannin/provigen/model/ForeignKeyConstraint.java
new file mode 100644
index 0000000..04d04ed
--- /dev/null
+++ b/ProviGenLib/src/com/tjeannin/provigen/model/ForeignKeyConstraint.java
@@ -0,0 +1,44 @@
+package com.tjeannin.provigen.model;
+
+/**
+ * Created by Dre on 14.04.2016.
+ *
+ */
+public class ForeignKeyConstraint {
+
+    private String column;
+    private String tableReferenced;
+    private String columnReferenced;
+
+    public ForeignKeyConstraint() {}
+
+    public ForeignKeyConstraint(String column, String tableReferenced, String columnReferenced) {
+        this.column = column;
+        this.tableReferenced = tableReferenced;
+        this.columnReferenced = columnReferenced;
+    }
+
+    public String getColumn() {
+        return column;
+    }
+
+    public void setColumn(String column) {
+        this.column = column;
+    }
+
+    public String getTableReferenced() {
+        return tableReferenced;
+    }
+
+    public void setTableReferenced(String tableReferenced) {
+        this.tableReferenced = tableReferenced;
+    }
+
+    public String getColumnReferenced() {
+        return columnReferenced;
+    }
+
+    public void setColumnReferenced(String columnReferenced) {
+        this.columnReferenced = columnReferenced;
+    }
+}
diff --git a/ProviGenLib/src/com/tjeannin/provigen/model/JoinEntity.java b/ProviGenLib/src/com/tjeannin/provigen/model/JoinEntity.java
new file mode 100644
index 0000000..d778259
--- /dev/null
+++ b/ProviGenLib/src/com/tjeannin/provigen/model/JoinEntity.java
@@ -0,0 +1,73 @@
+package com.tjeannin.provigen.model;
+
+import android.net.Uri;
+
+/**
+ * This model needed to execute a join-query
+ *
+ * Created by Dre on 07.04.2016.
+ */
+public class JoinEntity {
+
+    private Uri contentUri;
+    private String leftField;
+    private String rightField;
+
+    public JoinEntity() { }
+
+    /**
+     * For cross join.
+     * @param contentUri URI of right join table
+     */
+    public JoinEntity(Uri contentUri) {
+        this.contentUri = contentUri;
+    }
+
+    /**
+     * @param contentUri URI of right join table
+     * @param leftField Name of left field
+     * @param rightField Name of right field
+     */
+    public JoinEntity(Uri contentUri, String leftField, String rightField) {
+        this.contentUri = contentUri;
+        this.leftField = leftField;
+        this.rightField = rightField;
+    }
+
+    public Uri getContentUri() {
+        return contentUri;
+    }
+
+    public void setContentUri(Uri contentUri) {
+        this.contentUri = contentUri;
+    }
+
+    public String getLeftField() {
+        return leftField;
+    }
+
+    public void setLeftField(String leftField) {
+        this.leftField = leftField;
+    }
+
+    public String getRightField() {
+        return rightField;
+    }
+
+    public void setRightField(String rightField) {
+        this.rightField = rightField;
+    }
+
+    public String getTableName() {
+        return contentUri.getLastPathSegment();
+    }
+
+    @Override
+    public String toString() {
+        return "JoinEntity{" +
+                "contentUri=" + contentUri +
+                ", leftField='" + leftField + '\'' +
+                ", rightField='" + rightField + '\'' +
+                '}';
+    }
+}
diff --git a/ProviGenSample/AndroidManifest.xml b/ProviGenSample/AndroidManifest.xml
index 46f3175..d4110c3 100644
--- a/ProviGenSample/AndroidManifest.xml
+++ b/ProviGenSample/AndroidManifest.xml
@@ -1,32 +1,33 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-          package="com.tjeannin.provigen.sample"
-          android:versionCode="1"
-          android:versionName="1.0">
+    package="com.tjeannin.provigen.sample"
+    android:versionCode="1"
+    android:versionName="1.0">
 
     <uses-sdk
-            android:minSdkVersion="16"
-            android:targetSdkVersion="19"/>
+        android:minSdkVersion="15"
+        android:targetSdkVersion="23"/>
 
     <application
-            android:allowBackup="false"
-            android:icon="@drawable/ic_launcher"
-            android:label="@string/app_name"
-            android:theme="@style/AppTheme">
+        android:allowBackup="false"
+        android:icon="@drawable/ic_launcher"
+        android:label="@string/app_name"
+        android:theme="@style/AppTheme">
+
         <activity
-                android:name=".MainActivity"
-                android:label="@string/title_activity_main">
+            android:name=".MainActivity"
+            android:label="@string/app_name">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN"/>
-
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
 
         <provider
-                android:name="com.tjeannin.provigen.sample.SampleContentProvider"
-                android:authorities="com.tjeannin.provigen.sample"
-                android:exported="false">
+            android:name="com.tjeannin.provigen.sample.SampleContentProvider"
+            android:authorities="com.tjeannin.provigen.sample"
+            android:exported="false">
         </provider>
+
     </application>
 
 </manifest>
\ No newline at end of file
diff --git a/ProviGenSample/build.gradle b/ProviGenSample/build.gradle
index d21758c..d83bc63 100644
--- a/ProviGenSample/build.gradle
+++ b/ProviGenSample/build.gradle
@@ -1,7 +1,12 @@
 
 android {
-    buildToolsVersion "19.1.0"
-    compileSdkVersion 19
+    buildToolsVersion "23.0.3"
+    compileSdkVersion 23
+
+    dependencies {
+        compile 'com.android.support:support-v4:23.3.0'
+    }
+
     sourceSets {
         main {
             manifest.srcFile 'AndroidManifest.xml'
diff --git a/ProviGenSample/project.properties b/ProviGenSample/project.properties
index ed6ad53..a3fff05 100644
--- a/ProviGenSample/project.properties
+++ b/ProviGenSample/project.properties
@@ -11,5 +11,5 @@
 #proguard.config=${sdk.dir}/tools/proguard/proguard-android.txt:proguard-project.txt
 
 # Project target.
-target=android-19
+target=android-23
 
diff --git a/ProviGenSample/res/layout/person_item.xml b/ProviGenSample/res/layout/person_item.xml
index 7953f35..402acf3 100644
--- a/ProviGenSample/res/layout/person_item.xml
+++ b/ProviGenSample/res/layout/person_item.xml
@@ -1,20 +1,29 @@
-<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
-                android:layout_width="match_parent"
-                android:layout_height="match_parent"
-                android:orientation="vertical">
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="horizontal">
 
     <TextView
-            android:id="@+id/person_name"
-            android:layout_width="wrap_content"
-            android:layout_height="wrap_content"
-            android:textStyle="bold"
-            android:padding="5dp"/>
+        android:id="@+id/person_name"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:minWidth="90dp"
+        android:textStyle="bold"
+        android:padding="10dp"
+        android:text="Name"/>
 
     <TextView
-            android:id="@+id/person_age"
-            android:layout_width="wrap_content"
-            android:layout_height="wrap_content"
-            android:layout_toRightOf="@id/person_name"
-            android:padding="5dp"/>
+        android:id="@+id/person_age"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:padding="10dp"
+        android:text="25"/>
 
-</RelativeLayout>
\ No newline at end of file
+    <TextView
+        android:id="@+id/person_spec"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:padding="10dp"
+        android:text="Specialty"/>
+
+</LinearLayout>
\ No newline at end of file
diff --git a/ProviGenSample/src/com/tjeannin/provigen/sample/MainActivity.java b/ProviGenSample/src/com/tjeannin/provigen/sample/MainActivity.java
index b882fef..5c4eef0 100644
--- a/ProviGenSample/src/com/tjeannin/provigen/sample/MainActivity.java
+++ b/ProviGenSample/src/com/tjeannin/provigen/sample/MainActivity.java
@@ -2,6 +2,7 @@
 
 import android.content.ContentValues;
 import android.database.Cursor;
+import android.net.Uri;
 import android.os.Bundle;
 import android.support.v4.app.FragmentActivity;
 import android.support.v4.app.LoaderManager.LoaderCallbacks;
@@ -13,8 +14,14 @@
 import android.view.View.OnClickListener;
 import android.widget.ListView;
 
+import com.tjeannin.provigen.helper.ContractUtil;
+import com.tjeannin.provigen.helper.ProviGenUriBuilder;
+import com.tjeannin.provigen.model.JoinEntity;
+
 public class MainActivity extends FragmentActivity implements LoaderCallbacks<Cursor>, OnClickListener {
 
+    private static final String[] NAMES = {"David", "Stephanie", "John", "Anna", "Thomas", "Natalie", "Andrew", "Sofia", "Richard", "Alexandra", "Matthew", "Grace", "Christian", "Mary"};
+    private static final String[] SPECIALTIES = {"Android Developer", "iOS Developer", "Backend Developer", "Frontend Developer", "Web Developer", "Software Tester", "System Administrator", "Graphic Designer", "Project Manager", "Team Lead", "CEO"};
     private SimpleCursorAdapter adapter;
 
     @Override
@@ -23,12 +30,17 @@ public void onCreate(Bundle savedInstanceState) {
         setContentView(R.layout.activity_main);
 
         String[] columns = new String[]{
-                SampleContentProvider.Person.AGE,
-                SampleContentProvider.Person.NAME};
+                SampleContract.Person.AGE,
+                // important for correct obtaining of the columns
+                ContractUtil.joinName(SampleContract.Person.TABLE_NAME, SampleContract.Person.NAME),
+                ContractUtil.joinName(SampleContract.Specialty.TABLE_NAME, SampleContract.Specialty.NAME)
+        };
 
         int[] ids = {
                 R.id.person_age,
-                R.id.person_name};
+                R.id.person_name,
+                R.id.person_spec
+        };
 
         adapter = new SimpleCursorAdapter(this, R.layout.person_item, null, columns, ids, 0);
 
@@ -37,6 +49,7 @@ public void onCreate(Bundle savedInstanceState) {
         findViewById(R.id.add).setOnClickListener(this);
         findViewById(R.id.delete).setOnClickListener(this);
 
+        initSpecialties();
         getSupportLoaderManager().initLoader(0, null, this);
     }
 
@@ -46,9 +59,39 @@ public boolean onCreateOptionsMenu(Menu menu) {
         return true;
     }
 
+    private void initSpecialties() {
+        ContentValues[] valuesArray = new ContentValues[SPECIALTIES.length];
+        for(int i = 0; i < SPECIALTIES.length; i++) {
+            ContentValues values = new ContentValues();
+            values.put(SampleContract.Specialty.ID, i);
+            values.put(SampleContract.Specialty.NAME, SPECIALTIES[i]);
+            valuesArray[i] = values;
+        }
+        getContentResolver().bulkInsert(SampleContract.Specialty.CONTENT_URI, valuesArray);
+    }
+
+    private void addPerson() {
+        ContentValues values = new ContentValues();
+        values.put(SampleContract.Person.AGE, (int) (Math.random() * 40 + 20));
+        values.put(SampleContract.Person.NAME, NAMES[(int) (Math.random() * NAMES.length)]);
+        values.put(SampleContract.Person.SPECIALTY_ID, (int) (Math.random() * SPECIALTIES.length));
+        getContentResolver().insert(SampleContract.Person.CONTENT_URI, values);
+    }
+
+    private void clearPerson() {
+        getContentResolver().delete(SampleContract.Person.CONTENT_URI, null, null);
+    }
+
     @Override
     public Loader<Cursor> onCreateLoader(int id, Bundle args) {
-        return new CursorLoader(this, SampleContentProvider.Person.CONTENT_URI, null, "", null, "");
+        // create special join URI and execute the query
+        Uri innerJoinUri = ProviGenUriBuilder.joinUri(
+                ProviGenUriBuilder.JoinType.INNER_JOIN,
+                SampleContract.Person.CONTENT_URI,
+                new JoinEntity(SampleContract.Specialty.CONTENT_URI, SampleContract.Person.SPECIALTY_ID , SampleContract.Specialty.ID)
+        );
+
+        return new CursorLoader(this, innerJoinUri, SampleContract.Person.JOIN_PROJECTION, null, null, null);
     }
 
     @Override
@@ -66,17 +109,14 @@ public void onClick(View view) {
 
         switch (view.getId()) {
             case R.id.add:
-                ContentValues values = new ContentValues();
-                values.put(SampleContentProvider.Person.AGE, 20);
-                values.put(SampleContentProvider.Person.NAME, "Some Name");
-                getContentResolver().insert(SampleContentProvider.Person.CONTENT_URI, values);
+                addPerson();
                 break;
 
             case R.id.delete:
-                getContentResolver().delete(SampleContentProvider.Person.CONTENT_URI, "", null);
+                clearPerson();
                 break;
-            default:
 
+            default:
                 break;
         }
 
diff --git a/ProviGenSample/src/com/tjeannin/provigen/sample/SampleContentProvider.java b/ProviGenSample/src/com/tjeannin/provigen/sample/SampleContentProvider.java
index f141dd6..ae33243 100644
--- a/ProviGenSample/src/com/tjeannin/provigen/sample/SampleContentProvider.java
+++ b/ProviGenSample/src/com/tjeannin/provigen/sample/SampleContentProvider.java
@@ -1,37 +1,58 @@
 package com.tjeannin.provigen.sample;
 
 import android.content.Context;
+import android.database.sqlite.SQLiteDatabase;
 import android.database.sqlite.SQLiteOpenHelper;
-import android.net.Uri;
-import com.tjeannin.provigen.ProviGenBaseContract;
+
 import com.tjeannin.provigen.ProviGenOpenHelper;
 import com.tjeannin.provigen.ProviGenProvider;
-import com.tjeannin.provigen.annotation.Column;
-import com.tjeannin.provigen.annotation.Column.Type;
-import com.tjeannin.provigen.annotation.ContentUri;
 
 
 public class SampleContentProvider extends ProviGenProvider {
 
+    public static final String AUTHORITY = "com.tjeannin.provigen.sample";
+
+    public static final String DB_NAME = "ProviGenDatabase";
+    public static final int DB_VERSION = 1;
+
+    public static final String SECOND_DB_NAME = "ProviGenDatabaseSecond";
+    public static final int SECOND_DB_VERSION = 1;
+
+    private static final Class[] CONTRACTS = new Class[] {
+            SampleContract.Person.class,
+            SampleContract.Specialty.class,
+            SampleContract.Passport.class
+    };
+
+    private static final Class[] CONTRACTS_SECOND = new Class[] {
+            SampleContract.PersonSecondDb.class
+    };
+
     @Override
     public SQLiteOpenHelper openHelper(Context context) {
-        return new ProviGenOpenHelper(getContext(), "ProviGenDatabase", null, 1, new Class[]{Person.class});
+        return null; // you can return null
     }
 
     @Override
-    public Class[] contractClasses() {
-        return new Class[]{Person.class};
+    public SQLiteOpenHelper[] openHelpers(Context context) {
+        return new SQLiteOpenHelper[] {
+                new ProviGenOpenHelper(getContext(), DB_NAME, null, DB_VERSION, CONTRACTS), // first db
+                new ProviGenOpenHelper(getContext(), SECOND_DB_NAME, null, SECOND_DB_VERSION, CONTRACTS_SECOND) // second db
+        };
     }
 
-    public static interface Person extends ProviGenBaseContract {
-
-        @Column(Type.INTEGER)
-        public static final String AGE = "int";
+    @Override
+    public Class[] contractClasses() {
+        return null; // you can return null
+    }
 
-        @Column(Type.TEXT)
-        public static final String NAME = "string";
+    @Override
+    public Class[][] contractClassesMultipleDb() {
+        return new Class[][] {CONTRACTS, CONTRACTS_SECOND};
+    }
 
-        @ContentUri
-        public static final Uri CONTENT_URI = Uri.parse("content://com.tjeannin.provigen.sample/persons");
+    @Override
+    public int conflictAlgorithm() {
+        return SQLiteDatabase.CONFLICT_REPLACE;
     }
 }
diff --git a/ProviGenSample/src/com/tjeannin/provigen/sample/SampleContract.java b/ProviGenSample/src/com/tjeannin/provigen/sample/SampleContract.java
new file mode 100644
index 0000000..6d05c91
--- /dev/null
+++ b/ProviGenSample/src/com/tjeannin/provigen/sample/SampleContract.java
@@ -0,0 +1,108 @@
+package com.tjeannin.provigen.sample;
+
+import android.net.Uri;
+
+import com.tjeannin.provigen.ProviGenBaseContract;
+import com.tjeannin.provigen.annotation.Column;
+import com.tjeannin.provigen.annotation.ContentUri;
+import com.tjeannin.provigen.annotation.ForeignKey;
+import com.tjeannin.provigen.annotation.Id;
+import com.tjeannin.provigen.helper.ContractUtil;
+import com.tjeannin.provigen.helper.ProviGenUriBuilder;
+
+/**
+ * Created by Dre on 11.04.2016.
+ *
+ */
+public class SampleContract {
+
+    public static class Person implements ProviGenBaseContract {
+
+        public static final String TABLE_NAME = "person";
+
+        @Column(Column.Type.INTEGER)
+        public static final String AGE = "age";
+
+        @Column(Column.Type.TEXT)
+        public static final String NAME = "name";
+
+        @ForeignKey(table = Specialty.TABLE_NAME, column = Specialty.ID)
+        @Column(Column.Type.INTEGER)
+        public static final String SPECIALTY_ID = "specialty_id";
+
+        @ContentUri
+        public static final Uri CONTENT_URI = ProviGenUriBuilder.contentUri(SampleContentProvider.AUTHORITY, TABLE_NAME);
+
+        public static final String[] DEFAULT_PROJECTION = new String[] { _ID, AGE, NAME };
+
+        public static final String[] JOIN_PROJECTION = new String[] {
+                _ID,
+                AGE,
+                // ContractUtil.fullName() used to avoid ambiguous column name
+                ContractUtil.fullName(TABLE_NAME, NAME),
+                ContractUtil.fullName(Specialty.TABLE_NAME, Specialty.NAME)
+        };
+    }
+
+    // not implement ProviGenBaseContract interface (because non-autoincrement primary key)
+    public static class Specialty {
+
+        public static final String TABLE_NAME = "specialty";
+
+        @Id(autoincrement = false)
+        @Column(Column.Type.INTEGER)
+        public static final String ID = "id";
+
+        @Column(Column.Type.TEXT)
+        public static final String NAME = "name";
+
+        @ContentUri
+        public static final Uri CONTENT_URI = ProviGenUriBuilder.contentUri(SampleContentProvider.AUTHORITY, TABLE_NAME);
+
+        public static final String[] DEFAULT_PROJECTION = new String[] { ID, NAME };
+    }
+
+    // not implement ProviGenBaseContract interface (because non-autoincrement composite primary key)
+    public static class Passport {
+
+        public static final String TABLE_NAME = "passport";
+
+        @Id
+        @Column(Column.Type.TEXT)
+        public static final String SERIES = "series";
+
+        @Id
+        @Column(Column.Type.INTEGER)
+        public static final String NUMBER = "number";
+
+        @ContentUri
+        public static final Uri CONTENT_URI = ProviGenUriBuilder.contentUri(SampleContentProvider.AUTHORITY, TABLE_NAME);
+
+        public static final String[] DEFAULT_PROJECTION = new String[] {
+                SERIES,
+                NUMBER
+        };
+    }
+
+    /**
+     * Contract class for second database
+     */
+    public static class PersonSecondDb implements ProviGenBaseContract {
+
+        public static final String TABLE_NAME = "persons_second";
+
+        @Column(Column.Type.INTEGER)
+        public static final String AGE = "age";
+
+        @Column(Column.Type.TEXT)
+        public static final String NAME = "name";
+
+        @ContentUri
+        public static final Uri CONTENT_URI = ProviGenUriBuilder.contentUri(
+                SampleContentProvider.AUTHORITY,
+                TABLE_NAME,
+                SampleContentProvider.SECOND_DB_NAME); // name of second database
+
+        public static final String[] DEFAULT_PROJECTION = new String[] { _ID, AGE, NAME };
+    }
+}
diff --git a/ProviGenTests/build.gradle b/ProviGenTests/build.gradle
index 2d1a49f..d9f30f9 100644
--- a/ProviGenTests/build.gradle
+++ b/ProviGenTests/build.gradle
@@ -1,6 +1,6 @@
 android {
-    buildToolsVersion "19.1.0"
-    compileSdkVersion 19
+    buildToolsVersion "23.0.3"
+    compileSdkVersion 23
 
     sourceSets {
         main {
diff --git a/ProviGenTests/src/com/tjeannin/provigen/test/ExtendedProviderTestCase.java b/ProviGenTests/src/com/tjeannin/provigen/test/ExtendedProviderTestCase.java
index b93a09e..60fd086 100644
--- a/ProviGenTests/src/com/tjeannin/provigen/test/ExtendedProviderTestCase.java
+++ b/ProviGenTests/src/com/tjeannin/provigen/test/ExtendedProviderTestCase.java
@@ -2,8 +2,10 @@
 
 import android.content.ContentValues;
 import android.database.Cursor;
+import android.database.sqlite.SQLiteOpenHelper;
 import android.net.Uri;
 import android.test.ProviderTestCase2;
+
 import com.tjeannin.provigen.ProviGenOpenHelper;
 import com.tjeannin.provigen.ProviGenProvider;
 import com.tjeannin.provigen.annotation.Column;
@@ -61,11 +63,13 @@ protected void resetContractClasses(Class[] contractClasses) {
             getSuperClassField(getProvider(), "contracts").set(getProvider(), contracts);
 
             // Replace the open helper.
-            Field openHelperField = getSuperClassField(getProvider(), "openHelper");
-            ProviGenOpenHelper openHelper = (ProviGenOpenHelper) openHelperField.get(getProvider());
+            Field openHelpersField = getSuperClassField(getProvider(), "openHelpers");
+            ProviGenOpenHelper openHelper = (ProviGenOpenHelper) ((SQLiteOpenHelper[]) openHelpersField.get(getProvider()))[0];
             int version = getSuperClassField(openHelper, "mNewVersion").getInt(openHelper);
-            openHelperField.set(getProvider(), new ProviGenOpenHelper(
-                    getProvider().getContext(), "ProviGenDatabase", null, version + 1, contractClasses));
+            openHelpersField.set(
+                    getProvider(),
+                    new SQLiteOpenHelper[] {new ProviGenOpenHelper(getProvider().getContext(), "ProviGenDatabase", null, version + 1, contractClasses)}
+            );
 
         } catch (IllegalAccessException e) {
             e.printStackTrace();
diff --git a/ProviGenTests/src/com/tjeannin/provigen/test/basis/SimpleContentProvider.java b/ProviGenTests/src/com/tjeannin/provigen/test/basis/SimpleContentProvider.java
index dd1918a..5ad7830 100644
--- a/ProviGenTests/src/com/tjeannin/provigen/test/basis/SimpleContentProvider.java
+++ b/ProviGenTests/src/com/tjeannin/provigen/test/basis/SimpleContentProvider.java
@@ -24,15 +24,19 @@ public Class[] contractClasses() {
 
     public interface ContractOne extends ProviGenBaseContract {
 
+        String TABLE_NAME = "table_name_simple";
+
         @Column(Type.INTEGER)
         String MY_INT = "int";
 
         @ContentUri
-        Uri CONTENT_URI = Uri.parse("content://com.test.simple/table_name_simple");
+        Uri CONTENT_URI = Uri.parse("content://com.test.simple/" + TABLE_NAME);
     }
 
     public interface ContractTwo extends ProviGenBaseContract {
 
+        String TABLE_NAME = "table_name_simple";
+
         @Column(Type.INTEGER)
         String MY_INT = "int";
 
@@ -43,6 +47,6 @@ public interface ContractTwo extends ProviGenBaseContract {
         String MY_REAL = "real";
 
         @ContentUri
-        Uri CONTENT_URI = Uri.parse("content://com.test.simple/table_name_simple");
+        Uri CONTENT_URI = Uri.parse("content://com.test.simple/" + TABLE_NAME);
     }
 }
diff --git a/ProviGenTests/src/com/tjeannin/provigen/test/basis/SimpleContentProviderTest.java b/ProviGenTests/src/com/tjeannin/provigen/test/basis/SimpleContentProviderTest.java
index 83abd37..d883b81 100644
--- a/ProviGenTests/src/com/tjeannin/provigen/test/basis/SimpleContentProviderTest.java
+++ b/ProviGenTests/src/com/tjeannin/provigen/test/basis/SimpleContentProviderTest.java
@@ -6,6 +6,7 @@
 import android.database.sqlite.SQLiteDatabase;
 import android.net.Uri;
 import android.test.mock.MockContentResolver;
+
 import com.tjeannin.provigen.test.ExtendedProviderTestCase;
 import com.tjeannin.provigen.test.basis.SimpleContentProvider.ContractOne;
 import com.tjeannin.provigen.test.basis.SimpleContentProvider.ContractTwo;
@@ -16,10 +17,11 @@
 
 public class SimpleContentProviderTest extends ExtendedProviderTestCase<SimpleContentProvider> {
 
+    private static final String PROVIDER_AUTHORITY = "com.test.simple";
     private MockContentResolver contentResolver;
 
     public SimpleContentProviderTest() {
-        super(SimpleContentProvider.class, "com.test.simple");
+        super(SimpleContentProvider.class, PROVIDER_AUTHORITY);
     }
 
     @Override
@@ -41,16 +43,16 @@ public void testInsertQueryUpdateDelete() {
         // Update
         final ContentValues contentValues = new ContentValues(2);
         contentValues.put(ContractOne.MY_INT, 15);
-        contentResolver.update(ContractOne.CONTENT_URI, contentValues, "", null);
+        contentResolver.update(ContractOne.CONTENT_URI, contentValues, null, null);
 
         // Query
-        final Cursor cursor = contentResolver.query(ContractOne.CONTENT_URI, null, "", null, "");
+        final Cursor cursor = contentResolver.query(ContractOne.CONTENT_URI, null, null, null, null);
         cursor.moveToFirst();
         assertEquals(cursor.getInt(cursor.getColumnIndex(ContractOne.MY_INT)), 15);
         cursor.close();
 
         // Delete
-        contentResolver.delete(Uri.withAppendedPath(ContractOne.CONTENT_URI, String.valueOf(1)), "", null);
+        contentResolver.delete(Uri.withAppendedPath(ContractOne.CONTENT_URI, String.valueOf(1)), null, null);
         assertEquals(0, getRowCount(ContractOne.CONTENT_URI));
     }
 
@@ -99,7 +101,7 @@ public void testAutoIncrement() {
         contentResolver.insert(ContractOne.CONTENT_URI, getContentValues(ContractOne.class));
         contentResolver.insert(ContractOne.CONTENT_URI, getContentValues(ContractOne.class));
 
-        contentResolver.delete(Uri.withAppendedPath(ContractOne.CONTENT_URI, String.valueOf(3)), "", null);
+        contentResolver.delete(Uri.withAppendedPath(ContractOne.CONTENT_URI, String.valueOf(3)), null, null);
 
         contentResolver.insert(ContractOne.CONTENT_URI, getContentValues(ContractOne.class));
 
@@ -155,7 +157,7 @@ private List<String> getTableFields(final Uri contentUri) {
         final SQLiteDatabase sqLiteDatabase = getMockContext().openOrCreateDatabase("ProviGenDatabase", Context.MODE_PRIVATE, null);
         final String tableName = contentUri.getLastPathSegment();
         final Cursor rawQuery = sqLiteDatabase.rawQuery("PRAGMA table_info(" + tableName + ')', null);
-        final List<String> result = new ArrayList<String>(rawQuery.getCount());
+        final List<String> result = new ArrayList<>(rawQuery.getCount());
         if (rawQuery.moveToFirst()) {
             do {
                 result.add(rawQuery.getString(rawQuery.getColumnIndex("name")));
@@ -167,6 +169,6 @@ private List<String> getTableFields(final Uri contentUri) {
 
     public void testGetMimeType() {
         final String mimeType = getProvider().getType(ContractOne.CONTENT_URI);
-        assertEquals("vnd.android.cursor.dir/vdn.table_name_simple", mimeType);
+        assertEquals("vnd.android.cursor.dir/vdn." + PROVIDER_AUTHORITY + '.' + ContractOne.TABLE_NAME, mimeType);
     }
 }
diff --git a/ProviGenTests/src/com/tjeannin/provigen/test/multiple/MultipleContractContentProvider.java b/ProviGenTests/src/com/tjeannin/provigen/test/multiple/MultipleContractContentProvider.java
index cb9e0e9..d189e50 100644
--- a/ProviGenTests/src/com/tjeannin/provigen/test/multiple/MultipleContractContentProvider.java
+++ b/ProviGenTests/src/com/tjeannin/provigen/test/multiple/MultipleContractContentProvider.java
@@ -26,11 +26,13 @@ public Class[] contractClasses() {
 
     public static interface ContractOne extends ProviGenBaseContract {
 
+        String TABLE_NAME = "table_name_simple";
+
         @Column(Type.INTEGER)
         public static final String MY_INT = "int";
 
         @ContentUri
-        public static final Uri CONTENT_URI = Uri.parse("content://com.test.simple/table_name_simple");
+        public static final Uri CONTENT_URI = Uri.parse("content://com.test.simple/" + TABLE_NAME);
     }
 
     public static interface ContractTwo extends ProviGenBaseContract {
diff --git a/README.md b/README.md
index 4504eea..d117304 100644
--- a/README.md
+++ b/README.md
@@ -132,6 +132,201 @@ new TableBuilder(MyContract.class)
         .createTable(database);
 ```
 
+### Primary key and foreign key
+
+Autoincrement or non-autoincrement primary key.
+
+```java
+@Id(autoincrement = true)
+@Column(Column.Type.INTEGER)
+public static final String ID = "id";
+```
+
+Composite primary key support.
+
+```java
+public class Passport {
+
+    public static final String TABLE_NAME = "passport";
+    
+    @Id
+    @Column(Column.Type.TEXT)
+    public static final String SERIES = "series";
+    
+    @Id
+    @Column(Column.Type.INTEGER)
+    public static final String NUMBER = "number";
+    
+    @ContentUri
+    public static final Uri CONTENT_URI = ProviGenUriBuilder.contentUri(SampleContentProvider.AUTHORITY, TABLE_NAME);
+        
+}
+```
+
+Foreign key support.
+
+```java
+@ForeignKey(table = Specialty.TABLE_NAME, column = Specialty.ID)
+@Column(Column.Type.INTEGER)
+public static final String SPECIALTY_ID = "specialty_id";
+```
+
+### Multiple databases support
+
+Add a name of the second database in your ContractClass.
+
+```java
+public class PersonSecondDb implements ProviGenBaseContract {
+
+    public static final String TABLE_NAME = "persons_second";
+
+    @Column(Column.Type.INTEGER)
+    public static final String AGE = "age";
+
+    @Column(Column.Type.TEXT)
+    public static final String NAME = "name";
+
+    @ContentUri
+    public static final Uri CONTENT_URI = ProviGenUriBuilder.contentUri(
+            SampleContentProvider.AUTHORITY, 
+            TABLE_NAME, 
+            SampleContentProvider.SECOND_DB_NAME); // name of second database
+}
+```
+
+Override openHelpers(Context context) and contractClassesMultipleDb() methods in your content provider.
+
+```java
+public class SampleContentProvider extends ProviGenProvider {
+
+    public static final String AUTHORITY = "com.tjeannin.provigen.sample";
+
+    public static final String DB_NAME = "ProviGenDatabase";
+    public static final int DB_VERSION = 1;
+
+    public static final String SECOND_DB_NAME = "ProviGenDatabaseSecond";
+    public static final int SECOND_DB_VERSION = 1;
+
+    private static final Class[] CONTRACTS = new Class[] {
+            SampleContract.Person.class,
+            SampleContract.Specialty.class,
+            SampleContract.Passport.class
+    };
+
+    private static final Class[] CONTRACTS_SECOND = new Class[] {
+            SampleContract.PersonSecondDb.class
+    };
+
+    @Override
+    public SQLiteOpenHelper openHelper(Context context) {
+        return null; // you can return null
+    }
+
+    @Override
+    public SQLiteOpenHelper[] openHelpers(Context context) {
+        return new SQLiteOpenHelper[] {
+                new ProviGenOpenHelper(getContext(), DB_NAME, null, DB_VERSION, CONTRACTS), // first db
+                new ProviGenOpenHelper(getContext(), SECOND_DB_NAME, null, SECOND_DB_VERSION, CONTRACTS_SECOND) // second db
+        };
+    }
+
+    @Override
+    public Class[] contractClasses() {
+        return null; // you can return null
+    }
+
+    @Override
+    public Class[][] contractClassesMultipleDb() {
+        return new Class[][] {CONTRACTS, CONTRACTS_SECOND};
+    }
+}
+```
+
+### Joins support
+
+Inner join, left outer join and cross join support.
+Your ContractClasses.
+
+```java
+public static class Person implements ProviGenBaseContract {
+
+    public static final String TABLE_NAME = "person";
+
+    @Column(Column.Type.INTEGER)
+    public static final String AGE = "age";
+
+    @Column(Column.Type.TEXT)
+    public static final String NAME = "name";
+
+    @Column(Column.Type.INTEGER)
+    public static final String SPECIALTY_ID = "specialty_id";
+
+    @ContentUri
+    public static final Uri CONTENT_URI = ProviGenUriBuilder.contentUri(SampleContentProvider.AUTHORITY, TABLE_NAME);
+
+    public static final String[] DEFAULT_PROJECTION = new String[] { _ID, AGE, NAME };
+
+    // projection for join-query
+    public static final String[] JOIN_PROJECTION = new String[] {
+            _ID,
+            AGE,
+            // ContractUtil.fullName() used to avoid ambiguous column name
+            ContractUtil.fullName(TABLE_NAME, NAME),
+            ContractUtil.fullName(Specialty.TABLE_NAME, Specialty.NAME)
+    };
+}
+
+public static class Specialty {
+
+    public static final String TABLE_NAME = "specialty";
+
+    @Id
+    @Column(Column.Type.INTEGER)
+    public static final String ID = "id";
+
+    @Column(Column.Type.TEXT)
+    public static final String NAME = "name";
+
+    @ContentUri
+    public static final Uri CONTENT_URI = ProviGenUriBuilder.contentUri(SampleContentProvider.AUTHORITY, TABLE_NAME);
+
+    public static final String[] DEFAULT_PROJECTION = new String[] { ID, NAME };
+}
+```
+
+Use the method ContractUtil.joinName() for correct obtaining of the columns.
+
+```java
+String[] columns = new String[]{
+        SampleContract.Person.AGE,
+        // important for correct obtaining of the columns
+        ContractUtil.joinName(SampleContract.Person.TABLE_NAME, SampleContract.Person.NAME),
+        ContractUtil.joinName(SampleContract.Specialty.TABLE_NAME, SampleContract.Specialty.NAME)
+};
+
+int[] ids = {
+        R.id.person_age,
+        R.id.person_name,
+        R.id.person_spec
+};
+
+SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, R.layout.person_item, null, columns, ids, 0);
+```
+
+Create special join URI using the method ProviGenUriBuilder.joinUri() and execute the query.
+
+```java
+@Override
+public Loader<Cursor> onCreateLoader(int id, Bundle args) {
+    Uri innerJoinUri = ProviGenUriBuilder.joinUri(
+            ProviGenUriBuilder.JoinType.INNER_JOIN, // inner, left outer or cross join
+            SampleContract.Person.CONTENT_URI,
+            new JoinEntity(SampleContract.Specialty.CONTENT_URI, SampleContract.Person.SPECIALTY_ID , SampleContract.Specialty.ID));
+
+    return new CursorLoader(this, innerJoinUri, SampleContract.Person.JOIN_PROJECTION, null, null, null);
+}
+```
+
 ## License
 
 This content is released under the MIT License.
diff --git a/build.gradle b/build.gradle
index 9613b1f..907e98d 100644
--- a/build.gradle
+++ b/build.gradle
@@ -4,7 +4,7 @@ buildscript {
         mavenLocal()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:1.0.0'
+        classpath 'com.android.tools.build:gradle:2.0.0'
     }
 }
 
@@ -16,7 +16,7 @@ allprojects {
 }
 
 project(":ProviGenLib") {
-    apply plugin: "java"
+    apply plugin: 'java'
 
     dependencies {
         compile 'com.google.android:android:4.1.1.4'
@@ -24,16 +24,15 @@ project(":ProviGenLib") {
 }
 
 project(":ProviGenSample") {
-    apply plugin: "android"
+    apply plugin: 'com.android.application'
 
     dependencies {
         compile project(":ProviGenLib")
-        compile 'com.android.support:support-v4:21.0.3'
     }
 }
 
 project(":ProviGenTests") {
-    apply plugin: "android"
+    apply plugin: 'com.android.application'
 
     dependencies {
         compile project(":ProviGenLib")
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 7b6f538..1d4094d 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-2.2.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-2.11-all.zip