# Types of Sub-Queries

A sub-query is a query inside another query, in parentheses. An uncorrelated one runs once on its own; a correlated one uses the outer query's row and runs once per row.

![Cheat sheet: Types of Sub-Queries](https://fsdtrainingmedia.blob.core.windows.net/public/images/2026/11/bfef17ad13c74e5b971cd460ba87606d.webp)

- Category: SQL
- Level: Journeyman
- Tags: Correlated Subquery, sql, Subquery, t-sql
- Updated: November 3, 2026

Source: https://www.ask-codey.com/cheat-sheets/sub-queries-in-t-sql-types-of-sub-queries-cheat-sheet