Optimizing a stored function call in SELECT and WHERE clauses

Question

I have an SQL query with the following structure:

SELECT *, storedfunc(param, table.field) as f 
FROM table 
WHERE storedfunc(param, table.field) < value 
ORD         


        

Answer 1

Rewrite and test which one performs faster:

SELECT *, storedfunc(param, table.column) AS f 
FROM table 
WHERE storedfunc(param, table.column) < value 
ORDER BY f ;

SELECT *
FROM
  ( SELECT *, storedfunc(param, table.column) AS f 
    FROM table 
  ) AS tmp
WHERE f < value 
ORDER BY f ;

In MySQL, you can even write like this (warning: not standard SQL syntax):

SELECT *, storedfunc(param, table.column) AS f 
FROM table 
HAVING f < value 
ORDER BY f ;