Check Constraint:: ->to check values before accepting into a column with user defined condition at column level:: ================ >create table test1(eid int check(eid<5),ename varchar2(10)); EX:: SQL> create table test1(eid int check(eid<5),ename varchar2(10)); Table created. SQL> insert into test1 values(1,'dan'); 1 row created. SQL> insert into test1 values(2,'sam'); 1 row created. SQL> select * from test1; EID ENAME ---------- ---------- 1 dan 2 sam SQL> insert into test1 values(5,'sam'); insert into test1 values(5,'sam') * ERROR at line 1: ORA-02290: check constraint (SYSTEM.SYS_C007650) violated SQL> insert into test1 values(4,'sam'); 1 row created. SQL> select * from test1; EID ENAME ---------- ---------- 1 dan 2 sam 4 sam SQL> insert into test1 values(55,'sam'); insert into test1 values(55,'sam') * ERROR at line 1: ORA-02290