SQL EXISTS with Correlated Subquery

SQL EXISTS with Correlated Subquery is a SQL statement in the Subqueries category. EXISTS checks if a subquery returns any rows. Often faster than IN for large result sets. The syntax is SELECT * FROM t1 WHERE EXISTS (SELECT 1 FROM t2 WHERE t2.id = t1.id);. It returns existence check result. 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. A close relative is EXISTS, which returns TRUE if the subquery returns at least one row. Often faster than IN for large datasets. More about this category: Nested queries — correlated, EXISTS, IN, ANY, ALL, scalar subqueries. Related Subqueries entries: Scalar Subquery, Correlated Subquery, EXISTS, IN Subquery, ANY / ALL, DERIVED TABLE (Subquery in FROM), LATERAL Subquery (PostgreSQL), Subquery in SELECT.