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Implemented PIVOT / UNPIVOT table operators.
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‎CLAUDE.md‎

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@@ -138,6 +138,7 @@ Per-feature deep-dives live under `docs/claude/`. Each entry below is a trigger:
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- **`Cast` / coercion error paths** (CAST/CONVERT narrow targets, TRY_CAST/TRY_CONVERT swallow set, PARSE/TRY_PARSE culture-aware parsing) → [`casting.md`](docs/claude/casting.md).
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- **`Selection`, aggregates, window functions, set ops, CASE, OFFSET/FETCH** → [`query.md`](docs/claude/query.md).
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- **JOIN / APPLY** — INNER / LEFT / RIGHT / FULL / CROSS + CROSS/OUTER APPLY, ANSI-89 comma-FROM, EF `LeftJoin`/`RightJoin` routing (no LINQ `FullJoin`, so FULL is raw-SQL-only); `JoinDriver` equi-join hash fast path + `SqlValueKey` keying, nested-loop fallback, RIGHT/FULL materialization + derived-table-right, `JoinDiagnostics` strategy guard → [`joins.md`](docs/claude/joins.md).
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- **`PIVOT` / `UNPIVOT`** table operators — PIVOT desugars to grouped conditional aggregation (implicit grouping = all inner columns except FOR + aggregate-arg), UNPIVOT is a NULL-skipping unfold; both attach as a postfix FROM-source wrapper and ride the derived-table `LateralPlan` seam → [`pivot.md`](docs/claude/pivot.md).
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- **UPDATE / DELETE / INSERT…SELECT / SELECT…INTO / rowversion (incl. `@@DBTS` / `MIN_ACTIVE_ROWVERSION`) / identity helpers (`@@IDENTITY` / `SCOPE_IDENTITY` / `IDENT_CURRENT` / `IDENT_INCR` / `IDENT_SEED`) / `@@ROWCOUNT` / `ROWCOUNT_BIG` / OUTPUT / MERGE** → [`dml.md`](docs/claude/dml.md).
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- **Variables, control flow (IF/WHILE/BREAK/CONTINUE/RETURN), TRY/CATCH+THROW+ERROR_*, `@@ERROR` / `@@TRANCOUNT` / `XACT_STATE`, PRINT, WAITFOR** → [`control-flow.md`](docs/claude/control-flow.md).
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- **Cursors (`DECLARE … CURSOR` / `OPEN` / `FETCH` / `CLOSE` / `DEALLOCATE`, STATIC / KEYSET / DYNAMIC sensitivity, scroll fetches, `@@FETCH_STATUS` / `@@CURSOR_ROWS` / `CURSOR_STATUS`, `WHERE CURRENT OF`)** → [`cursors.md`](docs/claude/cursors.md).

‎SqlServerSimulator.Tests/PivotTests.cs‎

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using System.Data.Common;
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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 the <c>PIVOT</c> / <c>UNPIVOT</c> table operators.
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/// PIVOT desugars to grouped conditional aggregation (grouping key = every
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/// inner column except the FOR column and the aggregate argument), each IN
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/// value becoming <c>agg(CASE forCol WHEN value THEN argCol END)</c>; UNPIVOT
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/// unfolds each row into one row per non-NULL IN column. Both attach as a
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/// postfix to a FROM source and behave like a derived table downstream.
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/// Behavior probed against SQL Server 2025.
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/// </summary>
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[TestClass]
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public sealed class PivotTests
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{
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private static DbConnection SeededSales()
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{
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var connection = new Simulation().CreateOpenConnection();
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_ = connection.CreateCommand(
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"create table sales (Region varchar(10), Yr int, Amount decimal(10,2), Note varchar(20))").ExecuteNonQuery();
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_ = connection.CreateCommand(
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"insert sales values " +
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"('East', 2020, 100.00, 'a'), ('East', 2020, 50.00, 'a'), " +
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"('East', 2021, 200.00, 'b'), ('West', 2020, 10.00, 'a'), " +
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"('West', 2021, 20.00, 'b'), ('West', 2022, 5.00, 'c')").ExecuteNonQuery();
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return connection;
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}
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// === PIVOT ===
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[TestMethod]
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public void Pivot_DerivedTable_GroupsByRemainingColumn()
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{
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// Inner projection drops Note, so the grouping key is Region alone:
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// one row per region, each year folded into its own column.
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using var connection = SeededSales();
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const string pivot =
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"(select Region, Yr, Amount from sales) src " +
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"pivot (sum(Amount) for Yr in ([2020],[2021],[2022])) as p";
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AreEqual(2, connection.CreateCommand($"select count(*) from {pivot}").ExecuteScalar());
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AreEqual(150.00m, connection.CreateCommand($"select [2020] from {pivot} where Region = 'East'").ExecuteScalar());
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AreEqual(200.00m, connection.CreateCommand($"select [2021] from {pivot} where Region = 'East'").ExecuteScalar());
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AreEqual(5.00m, connection.CreateCommand($"select [2022] from {pivot} where Region = 'West'").ExecuteScalar());
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}
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[TestMethod]
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public void Pivot_StrayColumn_SplitsGroups()
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{
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// SELECT * over the bare table keeps Note, so (Region, Note) is the
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// implicit grouping key — East splits into the 'a' and 'b' groups.
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using var connection = SeededSales();
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AreEqual(5, connection.CreateCommand(
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"select count(*) from " +
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"(select Region, Note, Yr, Amount from sales) src " +
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"pivot (sum(Amount) for Yr in ([2020],[2021],[2022])) as p").ExecuteScalar());
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}
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[TestMethod]
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public void Pivot_EmptyGroup_SumIsNullCountIsZero()
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{
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using var connection = SeededSales();
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// East has no 2022 row for SUM → NULL...
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AreEqual(DBNull.Value, connection.CreateCommand(
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"select [2022] from (select Region, Yr, Amount from sales) src " +
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"pivot (sum(Amount) for Yr in ([2022])) as p where Region = 'East'").ExecuteScalar());
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// ...but COUNT over an empty group is 0, not NULL.
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AreEqual(0, connection.CreateCommand(
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"select [2022] from (select Region, Yr from sales) src " +
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"pivot (count(Yr) for Yr in ([2022])) as p where Region = 'East'").ExecuteScalar());
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}
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[TestMethod]
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public void Pivot_ValueNotInSource_ColumnOfNulls()
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{
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using var connection = SeededSales();
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AreEqual(DBNull.Value, connection.CreateCommand(
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"select [2099] from (select Region, Yr, Amount from sales) src " +
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"pivot (sum(Amount) for Yr in ([2099])) as p where Region = 'East'").ExecuteScalar());
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}
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[TestMethod]
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public void Pivot_StringForColumn()
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{
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using var connection = SeededSales();
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AreEqual(150.00m, connection.CreateCommand(
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"select [East] from (select Yr, Region, Amount from sales) src " +
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"pivot (sum(Amount) for Region in ([East],[West])) as p where Yr = 2020").ExecuteScalar());
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}
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[TestMethod]
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public void Pivot_AvgAggregate_WidensScale()
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{
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// AVG(decimal(10,2)) → decimal(38,6): East's 2020 avg of 100 and 50.
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using var connection = SeededSales();
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AreEqual(75.000000m, connection.CreateCommand(
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"select [2020] from (select Region, Yr, Amount from sales) src " +
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"pivot (avg(Amount) for Yr in ([2020])) as p where Region = 'East'").ExecuteScalar());
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}
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[TestMethod]
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public void Pivot_WhereAndOrderByApplyToOutput()
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{
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using var connection = SeededSales();
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using var reader = connection.CreateCommand(
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"select Region from (select Region, Yr, Amount from sales) src " +
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"pivot (sum(Amount) for Yr in ([2020],[2021])) as p " +
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"where [2020] > 50 order by [2020] desc").ExecuteReader();
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var regions = new List<string>();
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while (reader.Read()) regions.Add(reader.GetString(0));
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CollectionAssert.AreEqual(new[] { "East" }, regions);
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}
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[TestMethod]
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public void Pivot_ComputedForColumn_AdventureWorksShape()
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{
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// The shape of Sales.vSalesPersonSalesByFiscalYears: a derived table
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// projects YEAR(OrderDate) as the FOR column plus passthrough name
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// columns, pivoting SUM(SubTotal) across fiscal years.
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var connection = new Simulation().CreateOpenConnection();
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_ = connection.CreateCommand(
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"create table orders (SalesPersonId int, FullName varchar(20), OrderDate date, SubTotal decimal(10,2))").ExecuteNonQuery();
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_ = connection.CreateCommand(
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"insert orders values " +
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"(1, 'Amy', '2002-03-01', 100.00), (1, 'Amy', '2002-09-01', 50.00), " +
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"(1, 'Amy', '2003-01-01', 200.00), (2, 'Bob', '2004-06-01', 7.00)").ExecuteNonQuery();
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const string pivot =
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"(select SalesPersonId, FullName, year(OrderDate) as FiscalYear, SubTotal from orders) soh " +
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"pivot (sum(SubTotal) for FiscalYear in ([2002],[2003],[2004])) as pvt";
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AreEqual(150.00m, connection.CreateCommand(
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$"select [2002] from {pivot} where SalesPersonId = 1").ExecuteScalar());
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AreEqual(7.00m, connection.CreateCommand(
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$"select [2004] from {pivot} where FullName = 'Bob'").ExecuteScalar());
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AreEqual(DBNull.Value, connection.CreateCommand(
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$"select [2003] from {pivot} where FullName = 'Bob'").ExecuteScalar());
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connection.Dispose();
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}
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// === PIVOT error paths ===
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[TestMethod]
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public void Pivot_CountStar_Rejected()
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=> _ = new Simulation().AssertSqlError(
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"create table t (a int, b int); " +
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"select * from (select a, b from t) s pivot (count(*) for b in ([1])) p", 102);
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[TestMethod]
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public void Pivot_TwoAggregates_Rejected()
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=> _ = new Simulation().AssertSqlError(
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"create table t (a int, b int, c int); " +
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"select * from (select a, b, c from t) s pivot (sum(c), count(c) for b in ([1])) p", 102);
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[TestMethod]
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public void Pivot_MissingAlias_Rejected()
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=> _ = new Simulation().AssertSqlError(
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"create table t (a int, b int, c int); " +
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"select * from (select a, b, c from t) s pivot (sum(c) for b in ([1]))", 102);
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[TestMethod]
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public void Pivot_UnknownForColumn_Msg207()
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=> _ = new Simulation().AssertSqlError(
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"create table t (a int, b int, c int); " +
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"select * from (select a, b, c from t) s pivot (sum(c) for nope in ([1])) p", 207);
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[TestMethod]
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public void Pivot_DuplicateInValue_Msg8156()
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{
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var ex = new Simulation().AssertSqlError(
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"create table t (a int, b int, c int); " +
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"select * from (select a, b, c from t) s pivot (sum(c) for b in ([1],[1])) p", 8156);
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Contains("was specified multiple times for 'p'", ex.Message);
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}
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// === UNPIVOT ===
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private static DbConnection SeededQuarters()
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{
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var connection = new Simulation().CreateOpenConnection();
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_ = connection.CreateCommand(
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"create table q (ProductId int, Q1 int, Q2 int, Q3 int, Q4 int)").ExecuteNonQuery();
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_ = connection.CreateCommand(
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"insert q values (1, 10, 20, null, 40), (2, null, null, null, null), (3, 5, 6, 7, 8)").ExecuteNonQuery();
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return connection;
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}
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[TestMethod]
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public void Unpivot_ExcludesNullsAndAllNullRows()
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{
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using var connection = SeededQuarters();
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using var reader = connection.CreateCommand(
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"select ProductId, Quarter, Sales from q " +
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"unpivot (Sales for Quarter in (Q1, Q2, Q3, Q4)) as u " +
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"order by ProductId, Quarter").ExecuteReader();
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var rows = new List<(int, string, int)>();
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while (reader.Read())
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rows.Add((reader.GetInt32(0), reader.GetString(1), reader.GetInt32(2)));
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// Product 2 is all-NULL (vanishes); Product 1 drops its Q3 NULL.
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CollectionAssert.AreEqual(
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new[]
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{
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(1, "Q1", 10), (1, "Q2", 20), (1, "Q4", 40),
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(3, "Q1", 5), (3, "Q2", 6), (3, "Q3", 7), (3, "Q4", 8),
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},
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rows);
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}
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[TestMethod]
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public void Unpivot_SelectStar_ValueThenNameColumn()
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{
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// SELECT * order: passthrough, then value column, then name column.
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using var connection = SeededQuarters();
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using var reader = connection.CreateCommand(
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"select * from q unpivot (Sales for Quarter in (Q1, Q2, Q3, Q4)) as u").ExecuteReader();
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AreEqual("ProductId", reader.GetName(0));
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AreEqual("Sales", reader.GetName(1));
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AreEqual("Quarter", reader.GetName(2));
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}
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[TestMethod]
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public void Unpivot_TypeConflict_Msg8167()
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{
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var ex = new Simulation().AssertSqlError(
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"create table m (Id int, A bigint, B int); insert m values (1, 100, 2); " +
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"select Id, Col, Val from m unpivot (Val for Col in (A, B)) as u", 8167);
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Contains("conflicts with the type of other columns", ex.Message);
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}
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[TestMethod]
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public void Unpivot_MissingAlias_Rejected()
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=> _ = new Simulation().AssertSqlError(
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"create table q (ProductId int, Q1 int, Q2 int); " +
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"select * from q unpivot (Sales for Quarter in (Q1, Q2))", 102);
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[TestMethod]
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public void Unpivot_UnknownColumn_Msg207()
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=> _ = new Simulation().AssertSqlError(
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"create table q (ProductId int, Q1 int, Q2 int); " +
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"select * from q unpivot (Sales for Quarter in (Q1, Nope)) as u", 207);
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}

‎SqlServerSimulator/Errors/SimulatedSqlException.QueryErrors.cs‎

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@@ -46,6 +46,24 @@ internal static SimulatedSqlException SubqueryNotIntroducedWithExists() =>
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internal static SimulatedSqlException GroupingArgumentNotInGroupBy(int argumentIndex, string functionName = "GROUPING") =>
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new($"Argument {argumentIndex} of the {functionName} function does not match any of the expressions in the GROUP BY clause.", 8161, 16, 1);
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/// <summary>
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/// Mimics SQL Server's Msg 8156 — raised when a PIVOT's <c>IN</c> list
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/// names the same pivot value twice (each value becomes an output column,
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/// so a repeat is a duplicate column). <paramref name="pivotAlias"/> is
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/// the alias given to the PIVOT table source.
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/// </summary>
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internal static SimulatedSqlException PivotColumnSpecifiedMultipleTimes(string column, string pivotAlias) =>
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new($"The column '{column}' was specified multiple times for '{pivotAlias}'.", 8156, 16, 1);
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/// <summary>
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/// Mimics SQL Server's Msg 8167 — raised when the columns in an
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/// UNPIVOT's <c>IN</c> list don't all share one type (UNPIVOT folds them
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/// into a single value column, so their types must match). The
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/// conflicting column name is double-quoted in the message.
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/// </summary>
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internal static SimulatedSqlException UnpivotColumnTypeConflict(string column) =>
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new($"The type of column \"{column}\" conflicts with the type of other columns specified in the UNPIVOT list.", 8167, 16, 1);
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/// <summary>
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/// Mimics SQL Server's Msg 512 — fired when a scalar subquery (or one
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/// behind a comparison operator) returns more than one row. Verbatim

‎SqlServerSimulator/Parser/Expressions/AggregateExpression.cs‎

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_ => throw new InvalidOperationException($"Unknown aggregate kind {this.Kind}."),
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};
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/// <summary>
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/// Builds a single-operand aggregate programmatically (used by PIVOT
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/// desugaring, where each pivot column becomes
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/// <c>&lt;kind&gt;(CASE forCol WHEN value THEN argCol END)</c>). Bypasses
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/// the token parser and the <c>AggregateCollector</c> registration — the
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/// PIVOT planner hands the built list straight to
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/// <c>Selection.BuildSqlProjection</c>.
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/// </summary>
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internal static AggregateExpression CreatePivotAggregate(AggregateKind kind, Expression operand) =>
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new(kind, operand, distinct: false, separator: null);
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/// <summary>
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/// Convenience overload that auto-registers the new instance with the
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/// parser context's aggregate collector (when one is in scope, e.g.

‎SqlServerSimulator/Parser/Expressions/CaseExpression.cs‎

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this.elseBranch = elseBranch;
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}
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/// <summary>
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/// Builds a simple-form CASE programmatically — <c>CASE input WHEN
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/// compareValues[i] THEN thens[i] ... [ELSE elseBranch] END</c> — bypassing
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/// the token parser. Used by PIVOT desugaring, where each pivot column is
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/// <c>&lt;agg&gt;(CASE forCol WHEN value THEN argCol END)</c>; the
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/// simple-form <c>=</c> comparison aligns the value's type to the FOR
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/// column's via <see cref="BooleanExpression.CompareValuesPromoted"/>.
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/// </summary>
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internal static CaseExpression CreateSimple(Expression input, Expression[] compareValues, Expression[] thens, Expression? elseBranch) =>
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new(input, searchedWhens: null, compareValues, thens, elseBranch);
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public override SqlValue Run(RuntimeContext runtime)
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{
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var raw = this.input is null ? FindSearchedMatch(runtime) : FindSimpleMatch(runtime);

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