Update too slow !!!

Hi I have two tables (t1, t2) t1 t2 id recid col1 col2 t1.id is indexed primary key. It has 1,000,000 rows. t2.recid is indexed primary key. It has 50 rows. I have tried several queries below. They all take more than 3 minutes to update 50 rows in table t1. update t1 set col1 = 'A', col2 = 0 where t1.id in (select recid from t2) update t1 set col1 = 'A', col2 = 0 where exists (select recid from t2 where recid = t1.id) update t1 set col1 = 'A', col2 = 0 where exists (select 'a' from t2 where recid = t1.id) update t1 set col1 = 'A', col2 = 0 where t1.id = (select recid from t2 where recid = t1.id) update t1 set col1 = 'A', col2 = 0 where t1.id IN (select recid from t2 where recid = t1.id) It has to scan 1,000,000 rows in t1 table. How can I improve this Update query ? How can I let it scan the t2 instead of t1 table ? My machine is HP5900, 2 CPU, 1G of memory. DBMS is Informix 7.3.