How can my SQL query be optimized?

[shihawa]

I have a problem with a quite slowish MYSQL query. I'm building an AJAX menu with PHP and performance is really an issue. The query takes about 0,5 sec to complete, and i don't know how to optimize it. The SQL query :\[code\]SELECT M.nom_mat, M.id_mat, M.rang, SC.nom_sous_cat, SC.id_sous_cat, C.nom_cat,M.id_catFROM besson_mat MLEFT OUTER JOIN besson_lien_mat LM ON M.id_mat = LM.id_matLEFT OUTER JOIN besson_sous_cat SC ON SC.id_sous_cat = LM.id_sous_catLEFT OUTER JOIN besson_cat C ON C.id_cat = SC.id_catWHERE M.en_ligne = '1'AND M.lg = 'fr'AND (M.id_cat = '28'OR M.id_cat = '29')OR (SC.id_sous_cat = '37'OR SC.id_sous_cat = '42'OR SC.id_sous_cat = '43'OR SC.id_sous_cat = '44')ORDER BY C.id_cat ASC , SC.id_sous_cat ASC , M.rang ASC\[/code\]Thanks for your help, I'll update my question if you need more details.FINAL EDIT The extra parentheses in the WHERE clause were the cause of the problem. Now my Query takes about 0.0718 sec to complete, thank you so much.