Explain Common Table Expression(CTE) in SQL Server

Answer:

The common table expression (CTE) is a temporary named result set that you can reference within a SELECT, INSERT, UPDATE, or DELETE statement.
A CTE is defined with two parts:

A WITH clause containing a SELECT statement that generates a valid table
An outer SELECT statement that references the table expression.

The basic syntax structure for a CTE is:

WITH expression_name [ ( column_name [,...n] ) ] 

         AS

                ( CTE_query_definition )



        SELECT <column_list> FROM expression_name;