Step 16
4 min read

Reducing Subqueries

Learn when to replace subqueries with JOINs for better performance.

Subquery vs JOIN

Sometimes JOIN is faster than subquery.

Example

Slower (subquery):

SELECT * FROM students WHERE id IN (SELECT student_id FROM enrollments);

Faster (JOIN):

SELECT DISTINCT students.* FROM students JOIN enrollments ON students.id = enrollments.student_id;

Summary

Try JOIN instead of subquery Test both to see which is faster

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