Definition

correlated subquery

Contributor(s): Mark Fontecchio

A correlated subquery is a SQL query that depends on values executed by an outer query in order to complete. 

Because a correlated subquery requires the outer query to be executed first, the correlated subquery must run once for every row in the outer query. This causes correlated subqueries to be less efficient than other subqueries.

See also: correlation

 

This was last updated in September 2013

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