0 How To Use Subqueries In SQL

Introduction

In this article I am going to explain how to use Subqueries in SQL. A select statement known as subquery if it is codded within another SQL statement. Subquery can return a single value or a result set. This result set may contain a single column or more than one column.

There are four way to create subquery  in a SELECT statement.

• In WHERE Clause
• In HAVING Clause
• In FROM Clause
• In SELECT Clause

Example

select * from mcninvoices where invoicetotal > ( select avg(invoicetotal) from invoices )

Output  

Source : http://www.dotnetheaven.com/article/how-to-use-subqueries-in-sql