Common Table Expressions (CTE)
CTEs create temporary named result sets for use in queries.Use Cases
CTEs are useful for:- Breaking complex queries into readable parts
- Reusing the same subquery multiple times
- Recursive queries
Subqueries
Filter using results from another query.Example: Users with Orders
EXISTS
Check if a subquery returns any results.Set Operations
Combine results from multiple queries.UNION
Combine results, removing duplicates.UNION ALL
Combine results, keeping duplicates.INTERSECT
Return only rows that appear in both queries.EXCEPT
Return rows from first query that don’t appear in second.CASE Expressions
Conditional logic within queries. CASE must be used within GET expressions.Multiple Conditions
CASE in WHERE
Database Support
Complete Examples
Active Premium Users with Order Stats
Users Without Recent Orders
Categorized Products
Next Steps
Window Functions
ROW NUMBER, RANK, LAG, LEAD
Joins
Combine multiple tables

