Filtering on an alias in mysql

Question

Why doesn\'t the following query work? Mysql complains about z - can\'t I use an alias in the WHERE clause?

SELECT x + y AS z, t.*  FROM t
WHERE 
x = 1 and
z         


        

Answer 1

You should be aware that the usage of the HAVING clause without a GROUP BY clause is a non-standard extension of MySQL and won't work in other databases.

If you want this to be portable, you need to use a derived table:

SELECT *
FROM (
  SELECT (x + y) AS z, t.*  
  FROM t
  WHERE x = 1 
) t2
WHERE z = 2