SQL Use alias in Where statement

Question

I wounder how I could use an alias in a where statement.

Example :

SELECT SUBSTRING(Column1, 1, 4) + SUBSTRING(Column1, 4, 3)  AS Col1
FROM MyTable
WHERE Col1 = 'MySearch'

I use MSSQL 2005

Answer 1

You can use "having" instead of "where".

SELECT
    SUBSTRING(Column1, 1, 4) + SUBSTRING(Column1, 4, 3)  AS Col1
FROM
    MyTable
HAVING
    Col1 = 'MySearch'

Having do a "where" after execution of the query. Be careful to use it in the right conditions to have no performance problem.