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Implemented INDEX_COL, INDEXKEY_PROPERTY, STATS_DATE.
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10 files changed

Lines changed: 632 additions & 3 deletions

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‎CLAUDE.md‎

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@@ -149,7 +149,7 @@ Per-feature deep-dives live under `docs/claude/`. Each entry below is a trigger:
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- **CTE shapes / recursive-CTE error handling** → [`ctes.md`](docs/claude/ctes.md).
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- **JSON_VALUE / JSON_QUERY / JSON_MODIFY / JSON_OBJECT / JSON_ARRAY / JSON_PATH_EXISTS / ISJSON / OPENJSON** → [`json.md`](docs/claude/json.md).
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- **Name resolution, schema lookup, CREATE / DROP / ALTER SCHEMA TRANSFER, `OBJECT_ID` / `OBJECT_NAME` / `OBJECT_SCHEMA_NAME` / `SCHEMA_ID` / `SCHEMA_NAME` / `DB_ID` / `DB_NAME`, cross-DB read routing** → [`schemas.md`](docs/claude/schemas.md).
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- **System metadata surfaces** (sys.* / INFORMATION_SCHEMA.*, function-form lookups: `OBJECTPROPERTY` / `OBJECTPROPERTYEX` / `COLUMNPROPERTY` / `INDEXPROPERTY` / `TYPEPROPERTY` / `SERVERPROPERTY` / `COL_LENGTH` / `COL_NAME` / `TYPE_NAME` / `TYPE_ID` / `PARSENAME`) → [`catalog-views.md`](docs/claude/catalog-views.md).
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- **System metadata surfaces** (sys.* / INFORMATION_SCHEMA.*, function-form lookups: `OBJECTPROPERTY` / `OBJECTPROPERTYEX` / `COLUMNPROPERTY` / `INDEXPROPERTY` / `INDEX_COL` / `INDEXKEY_PROPERTY` / `STATS_DATE` / `TYPEPROPERTY` / `SERVERPROPERTY` / `COL_LENGTH` / `COL_NAME` / `TYPE_NAME` / `TYPE_ID` / `PARSENAME`) → [`catalog-views.md`](docs/claude/catalog-views.md).
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- **Scalar UDFs / TVFs / views / stored procs / dynamic SQL / `@@NESTLEVEL` / `@@PROCID`** → [`programmable.md`](docs/claude/programmable.md).
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- **`#foo` / `##foo` routing, DROP TABLE, TRUNCATE TABLE** → [`temp-tables.md`](docs/claude/temp-tables.md).
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- **`DECLARE @t TABLE`, table-variable DML, `OUTPUT … INTO`** → [`table-variables.md`](docs/claude/table-variables.md).

‎SqlServerSimulator.Tests/IndexIntrospectionTests.cs‎

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using static Microsoft.VisualStudio.TestTools.UnitTesting.Assert;
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namespace SqlServerSimulator;
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/// <summary>
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/// Behavioral tests for <c>INDEX_COL</c> / <c>INDEXKEY_PROPERTY</c> /
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/// <c>STATS_DATE</c>. Index_id resolution follows the same emission order
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/// as <c>sys.indexes</c> (PK=1, then UQ/named indexes sorted by ObjectId).
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/// Behaviors are probe-confirmed against SQL Server 2025 (2026-05-23);
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/// <c>STATS_DATE</c> intentionally diverges from real (which returns NULL
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/// when no auto-stats has run) — the simulator returns the table's
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/// <c>CreateDate</c> as a fake-but-realistic placeholder.
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/// </summary>
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[TestClass]
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public sealed class IndexIntrospectionTests
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{
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// === INDEX_COL ===
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[TestMethod]
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public void IndexCol_PK_FirstKeyColumn()
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=> AreEqual("id", new Simulation().ExecuteScalar(
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"create table t (id int primary key, name varchar(50)); " +
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"select index_col('t', 1, 1)"));
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[TestMethod]
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public void IndexCol_PK_OutOfRangeKeyId_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"create table t (id int primary key); " +
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"select index_col('t', 1, 2)"));
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[TestMethod]
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public void IndexCol_NamedIndex_FirstColumn()
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=> AreEqual("name", new Simulation().ExecuteScalar(
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"create table t (id int primary key, name varchar(50)); " +
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"create index ix_name on t(name); " +
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"select index_col('t', 2, 1)"));
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[TestMethod]
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public void IndexCol_CompositeIndex_BothColumns()
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{
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var sim = new Simulation();
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_ = sim.ExecuteNonQuery(
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"create table t (id int primary key, a int, b int); " +
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"create index ix_ab on t(a, b)");
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AreEqual("a", sim.ExecuteScalar("select index_col('t', 2, 1)"));
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AreEqual("b", sim.ExecuteScalar("select index_col('t', 2, 2)"));
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}
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[TestMethod]
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public void IndexCol_IncludeColumn_NotReachable()
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{
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// INCLUDE columns appear in sys.index_columns but INDEX_COL returns
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// NULL for them (key positions only). Probe-confirmed.
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var sim = new Simulation();
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_ = sim.ExecuteNonQuery(
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"create table t (id int primary key, a int, b int, c int); " +
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"create index ix_a on t(a) include (b, c)");
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AreEqual("a", sim.ExecuteScalar("select index_col('t', 2, 1)"));
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AreEqual(DBNull.Value, sim.ExecuteScalar("select index_col('t', 2, 2)"));
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}
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[TestMethod]
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public void IndexCol_UnknownIndexId_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"create table t (id int); " +
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"select index_col('t', 99, 1)"));
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[TestMethod]
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public void IndexCol_UnknownTable_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"select index_col('no_such_table', 1, 1)"));
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[TestMethod]
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public void IndexCol_NullTable_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar("select index_col(null, 1, 1)"));
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[TestMethod]
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public void IndexCol_NullIndexId_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"create table t (id int primary key); " +
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"select index_col('t', null, 1)"));
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[TestMethod]
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public void IndexCol_NullKeyId_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"create table t (id int primary key); " +
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"select index_col('t', 1, null)"));
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[TestMethod]
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public void IndexCol_KeyIdZero_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"create table t (id int primary key); " +
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"select index_col('t', 1, 0)"));
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[TestMethod]
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public void IndexCol_KeyIdNegative_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"create table t (id int primary key); " +
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"select index_col('t', 1, -1)"));
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[TestMethod]
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public void IndexCol_BracketedTableName()
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=> AreEqual("id", new Simulation().ExecuteScalar(
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"create table t (id int primary key); " +
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"select index_col('[dbo].[t]', 1, 1)"));
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[TestMethod]
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public void IndexCol_SchemaQualified()
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=> AreEqual("id", new Simulation().ExecuteScalar(
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"create table t (id int primary key); " +
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"select index_col('dbo.t', 1, 1)"));
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[TestMethod]
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public void IndexCol_DescendingKey_StillReturnsName()
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{
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// The DESC flag doesn't affect the returned column name.
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var sim = new Simulation();
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_ = sim.ExecuteNonQuery(
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"create table t (id int primary key, b varchar(20)); " +
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"create unique index ix_b on t(b desc)");
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AreEqual("b", sim.ExecuteScalar("select index_col('t', 2, 1)"));
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}
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// === INDEXKEY_PROPERTY ===
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[TestMethod]
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public void IndexKeyProperty_ColumnId_PK()
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=> AreEqual(1, new Simulation().ExecuteScalar(
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"create table t (id int primary key); " +
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"select indexkey_property(object_id('t'), 1, 1, 'ColumnId')"));
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[TestMethod]
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public void IndexKeyProperty_ColumnId_SecondaryIndex()
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=> AreEqual(2, new Simulation().ExecuteScalar(
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"create table t (id int primary key, name varchar(50)); " +
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"create index ix on t(name); " +
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"select indexkey_property(object_id('t'), 2, 1, 'ColumnId')"));
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[TestMethod]
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public void IndexKeyProperty_IsDescending_Ascending_Returns0()
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=> AreEqual(0, new Simulation().ExecuteScalar(
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"create table t (id int primary key, name varchar(50)); " +
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"create index ix on t(name); " +
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"select indexkey_property(object_id('t'), 2, 1, 'IsDescending')"));
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[TestMethod]
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public void IndexKeyProperty_IsDescending_Descending_Returns1()
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=> AreEqual(1, new Simulation().ExecuteScalar(
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"create table t (id int primary key, name varchar(50)); " +
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"create index ix on t(name desc); " +
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"select indexkey_property(object_id('t'), 2, 1, 'IsDescending')"));
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[TestMethod]
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public void IndexKeyProperty_IsDescending_PK_AlwaysZero()
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=> AreEqual(0, new Simulation().ExecuteScalar(
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"create table t (id int primary key); " +
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"select indexkey_property(object_id('t'), 1, 1, 'IsDescending')"));
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[TestMethod]
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public void IndexKeyProperty_CompositeIndex_SecondKeyDescending()
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=> AreEqual(1, new Simulation().ExecuteScalar(
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"create table t (id int primary key, a int, b int); " +
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"create index ix on t(a, b desc); " +
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"select indexkey_property(object_id('t'), 2, 2, 'IsDescending')"));
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[TestMethod]
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public void IndexKeyProperty_CompositeIndex_FirstKeyAscending()
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=> AreEqual(0, new Simulation().ExecuteScalar(
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"create table t (id int primary key, a int, b int); " +
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"create index ix on t(a, b desc); " +
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"select indexkey_property(object_id('t'), 2, 1, 'IsDescending')"));
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[TestMethod]
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public void IndexKeyProperty_OutOfRangeKeyId_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"create table t (id int primary key, name varchar(50)); " +
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"create index ix on t(name); " +
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"select indexkey_property(object_id('t'), 2, 99, 'ColumnId')"));
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[TestMethod]
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public void IndexKeyProperty_UnknownIndexId_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"create table t (id int); " +
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"select indexkey_property(object_id('t'), 99, 1, 'ColumnId')"));
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[TestMethod]
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public void IndexKeyProperty_UnknownObjectId_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"select indexkey_property(99999, 1, 1, 'ColumnId')"));
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[TestMethod]
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public void IndexKeyProperty_UnknownProperty_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"create table t (id int primary key); " +
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"select indexkey_property(object_id('t'), 1, 1, 'NotAProperty')"));
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[TestMethod]
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public void IndexKeyProperty_NullObjectId_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"select indexkey_property(null, 1, 1, 'ColumnId')"));
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[TestMethod]
203+
public void IndexKeyProperty_NullIndexId_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"create table t (id int primary key); " +
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"select indexkey_property(object_id('t'), null, 1, 'ColumnId')"));
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[TestMethod]
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public void IndexKeyProperty_NullKeyId_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"create table t (id int primary key); " +
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"select indexkey_property(object_id('t'), 1, null, 'ColumnId')"));
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[TestMethod]
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public void IndexKeyProperty_NullProperty_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"create table t (id int primary key); " +
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"select indexkey_property(object_id('t'), 1, 1, null)"));
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[TestMethod]
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public void IndexKeyProperty_CaseInsensitiveProperty()
222+
=> AreEqual(1, new Simulation().ExecuteScalar(
223+
"create table t (id int primary key); " +
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"select indexkey_property(object_id('t'), 1, 1, 'columnid')"));
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226+
[TestMethod]
227+
public void IndexKeyProperty_IncludeColumn_NotReachable()
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{
229+
// INCLUDE columns appear in sys.index_columns but
230+
// INDEXKEY_PROPERTY returns NULL for key positions beyond the
231+
// actual key column count.
232+
var sim = new Simulation();
233+
_ = sim.ExecuteNonQuery(
234+
"create table t (id int primary key, a int, b int); " +
235+
"create index ix on t(a) include (b)");
236+
AreEqual(DBNull.Value, sim.ExecuteScalar(
237+
"select indexkey_property(object_id('t'), 2, 2, 'ColumnId')"));
238+
}
239+
240+
// === STATS_DATE ===
241+
242+
[TestMethod]
243+
public void StatsDate_PK_ReturnsNonNullDateTime()
244+
{
245+
var sim = new Simulation();
246+
_ = sim.ExecuteNonQuery("create table t (id int primary key)");
247+
var v = sim.ExecuteScalar("select stats_date(object_id('t'), 1)");
248+
_ = IsInstanceOfType<DateTime>(v);
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IsGreaterThan(new DateTime(2020, 1, 1, 0, 0, 0, DateTimeKind.Unspecified), (DateTime)v!);
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}
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[TestMethod]
253+
public void StatsDate_NamedIndex_MatchesTableCreateDate()
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{
255+
var sim = new Simulation();
256+
_ = sim.ExecuteNonQuery(
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"create table t (id int primary key, a int); " +
258+
"create index ix on t(a)");
259+
var pk = (DateTime)sim.ExecuteScalar("select stats_date(object_id('t'), 1)")!;
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var ix = (DateTime)sim.ExecuteScalar("select stats_date(object_id('t'), 2)")!;
261+
AreEqual(pk, ix);
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}
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[TestMethod]
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public void StatsDate_UnknownIndexId_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"create table t (id int); " +
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"select stats_date(object_id('t'), 99)"));
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[TestMethod]
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public void StatsDate_UnknownObjectId_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"select stats_date(99999, 1)"));
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[TestMethod]
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public void StatsDate_NullObjectId_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar("select stats_date(null, 1)"));
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[TestMethod]
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public void StatsDate_NullStatsId_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"create table t (id int primary key); " +
283+
"select stats_date(object_id('t'), null)"));
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[TestMethod]
286+
public void StatsDate_HeapTable_NoIndex_Returns_Null()
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=> AreEqual(DBNull.Value, new Simulation().ExecuteScalar(
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"create table t (id int); " + // no PK = heap, index_id 0 is HEAP
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"select stats_date(object_id('t'), 1)"));
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}

‎SqlServerSimulator/Parser/Expression.cs‎

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Original file line numberDiff line numberDiff line change
@@ -663,6 +663,7 @@ private static Expression ResolveBuiltIn(string name, ParserContext context)
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"CONCAT_WS" => new StringConcat(context, StringConcatKind.ConcatWs),
664664
"COUNT_BIG" => AggregateExpression.Parse(context, AggregateKind.CountBig),
665665
"HOST_NAME" => new HostName(context),
666+
"INDEX_COL" => new IndexCol(context),
666667
"ISNUMERIC" => new IsNumeric(context),
667668
"OBJECT_ID" => new ObjectId(context),
668669
"PARSENAME" => new ParseName(context),
@@ -693,6 +694,7 @@ private static Expression ResolveBuiltIn(string name, ParserContext context)
693694
"LAST_VALUE" => WindowExpression.ParseLastValue(context),
694695
"LEFT_SHIFT" => new BitShift(context, isLeftShift: true),
695696
"ROW_NUMBER" => WindowExpression.ParseRowNumber(context),
697+
"STATS_DATE" => new StatsDate(context),
696698
"STRING_AGG" => AggregateExpression.Parse(context, AggregateKind.StringAgg),
697699
"SUSER_NAME" => new SUserName(context, isSidVariant: false),
698700
"XACT_STATE" => new XactState(context),
@@ -767,6 +769,7 @@ private static Expression ResolveBuiltIn(string name, ParserContext context)
767769
{
768770
"DATETIMEFROMPARTS" => new DatePartsBuilder(context, DatePartsBuilderKind.DateTimeFromParts),
769771
"HAS_PERMS_BY_NAME" => new HasPermsByName(context),
772+
"INDEXKEY_PROPERTY" => new IndexKeyProperty(context),
770773
"SYSDATETIMEOFFSET" => new CurrentTimeFunction(context, CurrentTimeKind.SysDateTimeOffset),
771774
"TRIGGER_NESTLEVEL" => new TriggerNestLevelFunction(context),
772775
_ => null

‎SqlServerSimulator/Parser/Expressions/IndexCol.cs‎

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using SqlServerSimulator.Storage;
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namespace SqlServerSimulator.Parser.Expressions;
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/// <summary>
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/// SQL <c>INDEX_COL('table', index_id, key_id)</c>: returns the
7+
/// <c>sysname</c> name of the key column at the <c>key_id</c>
8+
/// position (1-based) of the index identified by <c>index_id</c>.
9+
/// Returns NULL when the index doesn't exist, <c>key_id</c> is out of
10+
/// range, the <c>key_id</c> refers to an INCLUDE column (only key columns
11+
/// are reachable through this function), or any arg is NULL.
12+
/// Probe-confirmed wording / shape against SQL Server 2025 (2026-05-23).
13+
/// </summary>
14+
/// <remarks>
15+
/// The table-name argument follows the same dotted-string convention as
16+
/// <c>OBJECT_ID</c> — 1- to 4-part with optional bracket quoting,
17+
/// case-insensitive (reuses the same parser as <c>OBJECT_ID</c>).
18+
/// <c>index_id</c> resolution mirrors the
19+
/// <c>sys.indexes</c> emission order via <see cref="IndexLookup.ResolveByIndexId"/>.
20+
/// </remarks>
21+
internal sealed class IndexCol : Expression
22+
{
23+
private readonly Expression tableArg;
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private readonly Expression indexIdArg;
25+
private readonly Expression keyIdArg;
26+
27+
public IndexCol(ParserContext context)
28+
{
29+
this.tableArg = Parse(context);
30+
if (context.Token is not Tokens.Operator { Character: ',' })
31+
throw SimulatedSqlException.SyntaxErrorNear(context);
32+
this.indexIdArg = Parse(context.MoveNextRequiredReturnSelf());
33+
if (context.Token is not Tokens.Operator { Character: ',' })
34+
throw SimulatedSqlException.SyntaxErrorNear(context);
35+
this.keyIdArg = Parse(context.MoveNextRequiredReturnSelf());
36+
if (context.Token is not Tokens.Operator { Character: ')' })
37+
throw SimulatedSqlException.SyntaxErrorNear(context);
38+
}
39+
40+
public override SqlValue Run(RuntimeContext runtime)
41+
{
42+
var tableValue = this.tableArg.Run(runtime);
43+
var indexIdValue = this.indexIdArg.Run(runtime);
44+
var keyIdValue = this.keyIdArg.Run(runtime);
45+
if (tableValue.IsNull || indexIdValue.IsNull || keyIdValue.IsNull)
46+
return SqlValue.Null(SqlType.SystemName);
47+
48+
var tableName = tableValue.CoerceTo(SqlType.NVarchar).AsString;
49+
if (!ObjectId.TryParseObjectName(tableName, out var parsed)
50+
|| !runtime.Batch.TryResolveTable(parsed, out var table))
51+
{
52+
return SqlValue.Null(SqlType.SystemName);
53+
}
54+
55+
var indexId = indexIdValue.CoerceTo(SqlType.Int32).AsInt32;
56+
if (IndexLookup.ResolveByIndexId(table, indexId) is not { } resolved)
57+
return SqlValue.Null(SqlType.SystemName);
58+
59+
var keyId = keyIdValue.CoerceTo(SqlType.Int32).AsInt32;
60+
if (IndexLookup.GetKeyColumn(resolved.Constraint, resolved.Index, keyId) is not { } keyCol)
61+
return SqlValue.Null(SqlType.SystemName);
62+
63+
var columnId = IndexLookup.StorageOrdinalToColumnId(table, keyCol.StorageOrdinal);
64+
return columnId < 1 || columnId > table.Columns.Length
65+
? SqlValue.Null(SqlType.SystemName)
66+
: SqlValue.FromSystemName(table.Columns[columnId - 1].Name);
67+
}
68+
69+
public override SqlType GetSqlType(BatchContext batch, Func<MultiPartName, SqlType> resolveColumnType) => SqlType.SystemName;
70+
71+
internal override string DebugDisplay() =>
72+
$"INDEX_COL({this.tableArg.DebugDisplay()}, {this.indexIdArg.DebugDisplay()}, {this.keyIdArg.DebugDisplay()})";
73+
}

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