Add EXISTS, expand HAVING, fix formatting, mirror updates to zh-hans

README.md

@@ -51,7 +51,7 @@ Pull requests are welcome. Enjoy!
 * `LIKE` ‘%or%’ (find any values that have “or” in any position)
 * `LIKE` ‘_r%’ (find any values that have “r” in the second position)
 * `LIKE` ‘a_%_%’ (find any values that start with “a” and are at least 3 characters in length)
-* `LIKE` ‘[a-c]%’ (find any values starting with “a”, “b”, or “c”
+* `LIKE` ‘[a-c]%’ (find any values starting with “a”, “b”, or “c”)
 
 ### **IN**: operator that allows you to specify multiple values in a WHERE clause
 * essentially the IN operator is shorthand for multiple OR conditions
@@ -97,7 +97,12 @@ Pull requests are welcome. Enjoy!
 * `SELECT` column_name1, COUNT(column_name2) `FROM` table_name `WHERE` condition `GROUP BY` column_name1 `ORDER BY` COUNT(column_name2) DESC;
 
 ### **HAVING**: this clause was added to SQL because the WHERE keyword could not be used with aggregate functions
-* `SELECT` `COUNT`(column_name1), column_name2 `FROM` table `GROUP BY` column_name2 `HAVING` `COUNT(`column_name1`)` > 5;
+* `SELECT` `COUNT`(column_name1), column_name2 `FROM` table `GROUP BY` column_name2 `HAVING COUNT`(column_name1) > 5;
+* `SELECT` * `FROM` table_name `WHERE` column_name `IN` (`SELECT` column_name `FROM` table_name `GROUP BY` column_name `HAVING COUNT`(*) > 1);
+
+### **EXISTS**: used in a WHERE clause to check whether a subquery returns any rows
+* The `EXISTS` operator evaluates to true if the subquery returns at least one row, and false otherwise
+* `SELECT` * `FROM` table_name `WHERE EXISTS` (`SELECT` column_name `FROM` table_name `WHERE` condition);
 
 ### **WITH**: often used for retrieving hierarchical data or re-using temp result set several times in a query. Also referred to as "Common Table Expression"
 * `WITH RECURSIVE` cte `AS` (<br/>
@@ -128,17 +133,17 @@ Pull requests are welcome. Enjoy!
 # 3. Reporting Queries
 
 ### **COUNT**: returns the # of occurrences
-* `SELECT COUNT (DISTINCT` column_name`)`;
+* `SELECT COUNT` (`DISTINCT` column_name);
 
 ### **MIN() and MAX()**: returns the smallest/largest value of the selected column
-* `SELECT MIN (`column_names`) FROM` table_name `WHERE` condition;
-* `SELECT MAX (`column_names`) FROM` table_name `WHERE` condition;
+* `SELECT MIN` (column_names) `FROM` table_name `WHERE` condition;
+* `SELECT MAX` (column_names) `FROM` table_name `WHERE` condition;
 
 ### **AVG()**: returns the average value of a numeric column
-* `SELECT AVG (`column_name`) FROM` table_name `WHERE` condition;
+* `SELECT AVG` (column_name) `FROM` table_name `WHERE` condition;
 
 ### **SUM()**: returns the total sum of a numeric column
-* `SELECT SUM (`column_name`) FROM` table_name `WHERE` condition;
+* `SELECT SUM` (column_name) `FROM` table_name `WHERE` condition;
 
 <a name="joins"></a>
 # 4. Join Queries
@@ -154,7 +159,7 @@ Pull requests are welcome. Enjoy!
 * `SELECT` column_names `FROM` table1 `RIGHT JOIN` table2 `ON` table1.column_name=table2.column_name;
 
 ### **FULL (OUTER) JOIN**: returns all records when there is a match in either left or right table
-* `SELECT` column_names `FROM` table1 ``FULL OUTER JOIN`` table2 `ON` table1.column_name=table2.column_name;
+* `SELECT` column_names `FROM` table1 `FULL OUTER JOIN` table2 `ON` table1.column_name=table2.column_name;
 
 ### **Self JOIN**: a regular join, but the table is joined with itself
 * `SELECT` column_names `FROM` table1 T1, table1 T2 `WHERE` condition;

README_zh-hans.md

@@ -11,6 +11,7 @@
 4. [ 连接查询 ](#joins)
 5. [ 视图查询 ](#view)
 6. [ 修改表的查询 ](#alter)
+7. [ 创建表的查询。](#create)
 
 <a name="find"></a>
 # 1. 查找数据的查询
@@ -87,7 +88,12 @@
 * `SELECT` column_name1, COUNT(column_name2) `FROM` table_name `WHERE` condition `GROUP BY` column_name1 `ORDER BY` COUNT(column_name2) DESC;
 
 ### **HAVING**: HAVING 子句指定 SELECT 语句应仅返回聚合值满足指定条件的行。它被添加到 SQL 语言中，因为WHERE关键字不能与聚合函数一起使用。
-* `SELECT` `COUNT`(column_name1), column_name2 `FROM` table `GROUP BY` column_name2 `HAVING` `COUNT(`column_name1`)` > 5;
+* `SELECT` `COUNT`(column_name1), column_name2 `FROM` table `GROUP BY` column_name2 `HAVING COUNT`(column_name1) > 5;
+* `SELECT` * `FROM` table_name `WHERE` column_name `IN` (`SELECT` column_name `FROM` table_name `GROUP BY` column_name `HAVING COUNT`(*) > 1);
+
+### **EXISTS**: 用于 WHERE 子句中，检查子查询是否返回任何行
+* 如果子查询返回至少一行，`EXISTS` 运算符的结果为 true，否则为 false
+* `SELECT` * `FROM` table_name `WHERE EXISTS` (`SELECT` column_name `FROM` table_name `WHERE` condition);
 
 
 <a name="modify"></a>
@@ -109,17 +115,17 @@
 # 3. 聚合查询
 
 ### **COUNT**: 返回出现次数
-* `SELECT COUNT (DISTINCT` column_name`)`;
+* `SELECT COUNT` (`DISTINCT` column_name);
 
 ### **MIN() and MAX()**: 返回所选列的最小/最大值
-* `SELECT MIN (`column_names`) FROM` table_name `WHERE` condition;
-* `SELECT MAX (`column_names`) FROM` table_name `WHERE` condition;
+* `SELECT MIN` (column_names) `FROM` table_name `WHERE` condition;
+* `SELECT MAX` (column_names) `FROM` table_name `WHERE` condition;
 
 ### **AVG()**: 返回数字列的平均值
-* `SELECT AVG (`column_name`) FROM` table_name `WHERE` condition;
+* `SELECT AVG` (column_name) `FROM` table_name `WHERE` condition;
 
 ### **SUM()**: 返回数值列的总和
-* `SELECT SUM (`column_name`) FROM` table_name `WHERE` condition;
+* `SELECT SUM` (column_name) `FROM` table_name `WHERE` condition;
 
 <a name="joins"></a>
 # 4. 连接查询
@@ -135,7 +141,7 @@
 * `SELECT` column_names `FROM` table1 `RIGHT JOIN` table2 `ON` table1.column_name=table2.column_name;
 
 ### **FULL (OUTER) JOIN**: 全外连接，全连接是左右外连接的并集. 连接表包含被连接的表的所有记录, 如果缺少匹配的记录, 以 NULL 填充。
-* `SELECT` column_names `FROM` table1 ``FULL OUTER JOIN`` table2 `ON` table1.column_name=table2.column_name;
+* `SELECT` column_names `FROM` table1 `FULL OUTER JOIN` table2 `ON` table1.column_name=table2.column_name;
 
 ### **Self JOIN**: 自连接，表自身连接
 * `SELECT` column_names `FROM` table1 T1, table1 T2 `WHERE` condition;
@@ -164,8 +170,15 @@
 ### **DROP**: 删除字段
 * `ALTER TABLE` table_name `DROP COLUMN` column_name;
 
+<a name="create"></a>
+# 7. 创建表的查询
 
-
-
+### **CREATE**: 创建一张表
+* `CREATE TABLE` table_name `(` <br />
+   `column1` `datatype`, <br />
+   `column2` `datatype`, <br />
+   `column3` `datatype`, <br />
+   `column4` `datatype`, <br />
+   `);`