Repeat computation in WHERE and ORDER BY

pajakleon · #1 (**permalink**) 09-12-07, 03:51

Hi. I have question if MySQL computes the same intructions which are in WHERE, HAVING and ORDER BY clause two times or only one?

Example:
SELECT id FROM users
HAVING MATCH(tytul,opis,tags) AGAINST('doda') >0
ORDER BY MATCH(tytul,opis,tags) AGAINST('doda') DESC)

Will MySQL compute one or two times MATCH(tytul,opis,tags) AGAINST('doda') ?

aschk · #2 (**permalink**) 09-12-07, 05:00

I'm sure your statement should probably be :

Code:

SELECT id FROM users
HAVING MATCH(tytul,opis,tags) AGAINST('doda') >0
ORDER BY tytul,opis,tags DESC

However, having not tested this resultset I cannot say for sure this will give you the result you desire.
You might want to run EXPLAIN on this query to see what it does.