Hi! Q1. Is subquery better or join?
For subquery: SELECT t1.c1,(SELECT t2.c2 FROM t2 WHERE t2.c1 = t1.c1) FROM t1 I wonder it will loop n times if t1 returns n rows. If this is the case, is it better to use join like this: SELECT t1.c1,t2.c2 FROM t1,t2 WHERE t2.c1 = t1.c1 Q2. If the query is not optimize like this: SELECT t1.c1,t2.c2 FROM t1,t2,t1,t2,t2 WHERE t2.c1=t1.c1 AND t1.c1=t2.c1 AND t1.c1=t2.c1 and the size of this clause can soar up to several kbytes, then can this query cause performance problem? Regards, -- _______________________________________________ Get your free email from http://www.graffiti.net Powered by Outblaze ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
