Bonsoir à tous !

Je cherche a faire une requête un peu étrange, dans le but de minimiser au maximum le traitement en PHP. J'ai besoin pour cela d'un WHERE <condition> sachant que la <condition> varie en fonction de la valeur d'un champs...
Problème, la requete s'execute mais ne renvoie rien :

SELECT mp_threads.mp_thread_id, 
	mp_threads.mp_thread_starter_id, 
	mp_threads.mp_thread_dest_id, 
	mp_threads.mp_thread_subject, 
	mp_threads.mp_thread_starter_state, 
	mp_threads.mp_thread_dest_state, 
	mp_threads.mp_thread_date, 
	CASE WHEN mp_threads.mp_thread_starter_id = '.$_SESSION['mbr_id'].' THEN "starter" ELSE "dest" END AS mbr_role, 
	members_starter.mbr_id AS mbr_id_starter, 
	members_starter.mbr_pseudo AS mbr_pseudo_starter,
	members_dest.mbr_id AS mbr_id_dest, 
	members_dest.mbr_pseudo AS mbr_pseudo_dest 
	FROM mp_threads 
	LEFT JOIN members AS members_starter
	ON members_starter.mbr_id = mp_threads.mp_thread_starter_id 
	LEFT JOIN members AS members_dest 
	ON members_dest.mbr_id = mp_threads.mp_thread_dest_id
	WHERE (CASE WHEN mp_threads.mp_thread_starter_id = '.$_SESSION['mbr_id'].' THEN
		mp_thread_starter_state != 2 
	ELSE 
		mp_thread_dest_state != 2 
	END) 
	AND (mp_thread_starter_id = '.$_SESSION['mbr_id'].' OR mp_thread_dest_id = '.$_SESSION['mbr_id'].') 
	ORDER BY mp_thread_date DESC')

J'ai essayé avec un HAVING, qui me semblait plus logique, mais pareil : aucun résultat retourné, alors que ça devrait...

Merci de bien vouloir m'aider.