title: How can my SQL query be optimized?
body: <p>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. </p>
  
  <p><strong>The SQL query :</strong></p>
  
  <pre><code>SELECT M.nom_mat, M.id_mat, M.rang, SC.nom_sous_cat, SC.id_sous_cat, C.nom_cat,M.id_cat
  FROM besson_mat M
  LEFT OUTER JOIN besson_lien_mat LM ON M.id_mat = LM.id_mat
  LEFT OUTER JOIN besson_sous_cat SC ON SC.id_sous_cat = LM.id_sous_cat
  LEFT OUTER JOIN besson_cat C ON C.id_cat = SC.id_cat
  WHERE 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></pre>
  
  <p>Thanks for your help, I'll update my question if you need more details.</p>
  
  <p><strong>FINAL EDIT</strong> </p>
  
  <p>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. </p>