Transform UPDATE to MERGE + Replace CASE WHEN (SELECT with SELECT ...CASE WHEN ...

 Hi ,

I have to transform un "UPDATE" to "MERGE" to improve performances.

Il have also to do 

SELECT...CASE WHEN instead of CASE WHEN ...SELECT...after join of the 4 tables .

Regards ,

GD.

UPDATE PRODUITS P
SET  P.STATUS         = 'A'
    ,P.cd_type = (CASE WHEN (SELECT  1 FROM PARAM PRM  WHERE PRM.cd_par = 2012  AND PRM.cd_par = P.cd_par  AND PRM.id_auto = P.id_auto) = 1
                  THEN 'P1' 
				  ELSE (SELECT  MIN(D.cd_FLO) KEEP(DENSE_RANK FIRST ORDER BY D.no_ordre)
                                           FROM  DIR D,COM