Database Management Systems · Query languages

SQL subqueries

A query nested inside another query, used as a stand-in value or filter.

Also known as: nested queries, correlated subqueries.

Start a lesson on SQL subqueries

Learn first

• SQL joins: Combining rows from two or more tables based on a matching column.
• SQL aggregation and grouping: Collapsing many rows into one summary number per group, like a total or average per category.

Leads to

• Views and materialized views: A saved query that acts like a table; materialized means the result is actually stored, not recomputed each time.

Related topics

• Query processing and optimization: How the database decides which order to run joins and filters in, to answer a query as cheaply as possible.
• Views and materialized views: A saved query that acts like a table; materialized means the result is actually stored, not recomputed each time.