A subquery is a query that appears inside another query statement. Subqueries are also referred to as sub- SELECT s or nested SELECT s. The full SELECT syntax is valid in subqueries.

What is a sub query what are its types?

A subquery is a query within another query. The outer query is called as main query and inner query is called as subquery. The subquery generally executes first, and its output is used to complete the query condition for the main or outer query. Subquery must be enclosed in parentheses.

When would you use a sub query?

Use subqueries when the result that you want requires more than one query and each subquery provides a subset of the table involved in the query. If a membership question is asked, then a subquery is usually used.