What Is Meant by Correlated Query?

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.

What is correlated query with example?

In a SQL database query, a correlated subquery (also known as a synchronized subquery) is a subquery (a query nested inside another query) that uses values from the outer query. Because the subquery may be evaluated once for each row processed by the outer query, it can be slow.

Why we use correlated query?

Correlated subqueries are used for row-by-row processing. ... A correlated subquery is one way of reading every row in a table and comparing values in each row against related data. It is used whenever a subquery must return a different result or set of results for each candidate row considered by the main query.