Subqueries vs CTEs: Query Optimizer Internals & Memory Spooling Explained
Many engineers believe Common Table Expressions (CTEs) are always faster than subqueries. In modern SQL Server (and PostgreSQL), that is a myth . Here is what actually happens under the hood: 1.
- CTEs and subqueries treated similarly by SQL optimizer in recent versions
- CTEs offer readability and pipeline stacking advantages
- Reusing a CTE multiple times may cause performance overhead