Inline Subquery Performance
Inline Subquery Performance is a SQL statement in the Subqueries category. Performance of IN, EXISTS, and JOIN depends on data size, indexes, and NULL handling. Not always intuitive. The syntax is -- IN (subquery) vs EXISTS vs JOIN — performance considerations.. It returns performance guidance. A typical example: -- IN: best for small subquery results SELECT * FROM products WHERE category_id IN (SELECT id FROM categories WHERE active = 1); -- EXISTS: best for large subquery, correlated SELECT * FROM products p WHERE EXISTS ( SELECT 1 FROM categories c WHERE c.id = p.category_id AND c.active = 1 ); -- JOIN: best when both tables are large SELECT p.* FROM products p JOIN categories c ON p.category_id =… A close relative is Scalar Subquery, which a subquery that returns a single value (one row, one column). Can be used in SELECT, WHERE, HAVING clauses. A close relative is Correlated Subquery, which a subquery that references columns from the outer query. Evaluated for each row of the outer query.