SQL CTE and Subquery Interview Questions

Common SQL CTE and subquery interview patterns

• Multi-step transformations with CTEs
• Filtering on aggregated results
• Correlated subqueries for per-row logic
• Using CTEs to avoid repeated logic
• Anti-joins via NOT EXISTS
• Top N per group with subqueries

Common mistakes with CTEs and subqueries

• Forgetting to reference the CTE in the final query
• Correlated subqueries that return multiple rows
• Over-nesting when a CTE would be clearer
• Filtering too early or too late in the pipeline
• Assuming subqueries always outperform JOINs

How CTE and subquery questions are evaluated in interviews

Related SQL concepts

• SQL JOIN interview questions
• SQL aggregation interview questions
• SQL window function interview questions
• SQL NULL handling interview questions