Question

Consider the following SQL (SQL Server 2008) statement:

WITH MyResult AS
(
  SELECT 
    Name,
    Row_ID AS ORD
  FROM Person Where Gender = @Gender
)
SELECT *
FROM MyResult
WHERE ORD > 5

Is MyResult stored in a temporary table in the tempdb? Or does it do something else?

We are optimising some queries and would lke to better understand WITH statements (internally) to help gauge performance etc.

Thanks

Answer 1

No, as per this MSDN article

…the CTE is a language-level
construct—meaning that SQL Server does
not internally create temp or virtual
tables…

And also, as mentioned here:

A common table expression (CTE) can be
thought of as a temporary result set
that is defined within the execution
scope of a single SELECT, INSERT,
UPDATE, DELETE, or CREATE VIEW
statement. A CTE is similar to a
derived table in that it is not stored
as an object and lasts only for the
duration of the query.