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Intermediate About 25 min
Subqueries & EXISTS
Nest queries inside queries, use EXISTS for existence checks, and write correlated subqueries.
What you'll learn
- Write scalar subqueries that return a single value
- Use IN and NOT IN with subqueries for set membership
- Check row existence with EXISTS and NOT EXISTS
- Understand correlated subqueries that reference the outer query
- Choose between subqueries and JOINs for readability and performance