You don't write column for that. You write a trigger. -- Mladen Gogala Ext. 121 -----Original Message----- From: Lyndon Tiu [mailto:ltiu@xxxxxxxxxxxxx] Sent: Friday, December 03, 2004 2:47 PM To: oracle-l@xxxxxxxxxxxxx Subject: Check Contraint Question Hello, Could use some help here. Table1 has: Column1 varchar(32) is non-unique and Column2 number(1) with a constraint check (Column2 in ('0','1')) -- //www.freelists.org/webpage/oracle-l