Discovered by: /uber-report 2026-05-10 (SqlBuildingBlocks QA)

Context

CrossDialectParityTests.cs uses [Theory] + [MemberData] to verify the same SQL produces equivalent ASTs across all four grammar dialects. It covers basic SELECT, ORDER BY, GROUP BY/HAVING, INNER JOIN, INTERVAL window-frame bounds, and DML basics.

Waves 10 and 16 added CTE resolution and derived-table materialization. Each dialect''s integration tests exercise these independently, but no single [Theory] parses the same CTE or derived-table SQL through all four grammars and compares the resulting AST structures.

Proposed Work

Add to CrossDialectParityTests.cs:

1. Cte_NonRecursive_ProducesEquivalentAst — [Theory] over all 4 SelectGrammars; parses WITH x AS (SELECT a FROM tbl WHERE x > 1) SELECT a FROM x; asserts selectStmt.Ctes.Count == 1, CTE name, and selectStmt.Table is SqlCteTable.
2. DerivedTable_InFrom_ProducesEquivalentAst — [Theory] over all 4 SelectGrammars; parses SELECT dt.a FROM (SELECT a FROM tbl WHERE x > 1) AS dt; asserts FROM table is SqlDerivedTable with the expected inner table name.

Note: recursive CTE cross-dialect is a separate follow-up (dialect support not fully validated across all four).

Acceptance Criteria

• Both [Theory] methods cover all 4 grammar dialects in their MemberData
• CTE parity test asserts SqlCteTable type on the rewritten FROM reference
• Derived-table parity test asserts SqlDerivedTable type on the FROM reference
• All 8 new theory cases pass under dotnet test --configuration Release