Subqueries

Nest queries within other SQL statements. Learn to use scalar, column, row, and table subqueries to filter or calculate data dynamically.

Subqueries With ALL

Compare a value against all results from a subquery. The ALL operator returns TRUE if the comparison holds for every row returned by the subquery.

Subqueries With ANY and SOME

Compare a value against any result from a subquery. The ANY (or SOME) operator returns TRUE if the comparison holds for at least one row. IN can be used for =ANY.

Subqueries With EXISTS

Test for the existence of rows. The EXISTS operator returns TRUE if the subquery returns at least one row, often used for correlated subqueries.

Subqueries With JOINs

Understand when to use subqueries versus joins. This guide explains performance implications and how to rewrite subqueries as joins for efficiency.

Subqueries in a FROM Clause (Derived Tables)

Use a subquery as a temporary table. Derived tables allow you to select from the result set of another query within the FROM clause.

Row Subqueries

Retrieve a single row of multiple values. A row subquery returns a tuple that can be compared against a row constructor in the outer query.

Scalar Subqueries

Return a single value. A scalar subquery produces a one-row, one-column result that can be used anywhere a constant or expression is valid.

Subquery Limitations

Review restrictions on subquery usage. This page details unsupported operations, such as modifying a table while selecting from it in a subquery.