An interesting observation IN ignore null values as you can see in the table there are 310 null values in column TBL_DSM. SQL> select count(*) from daz.utl_tablas_me 2 where tbl_dsm in 3 (select null from daz.utl_tablas_me); COUNT(*) --------- 0 SQL> select count(*) from daz.utl_tablas_me 2 where exists(select null from daz.utl_tablas_me); COUNT(*) --------- 310 ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx put 'unsubscribe' in the subject line. -- Archives are at //www.freelists.org/archives/oracle-l/ FAQ is at //www.freelists.org/help/fom-serve/cache/1.html -----------------------------------------------------------------