Re: Modifying a constraint to make exceptions...

Just use a unique index...

SQL> CREATE TABLE TEST5 (C1 VARCHAR2(1)) 2 /

Table created.

SQL> CREATE UNIQUE INDEX TEST5_U1 ON TEST5(C1) 2 /

Index created.

SQL> INSERT INTO TEST5 VALUES (NULL)
2 /

1 row created.

SQL> INSERT INTO TEST5 VALUES (NULL)
2 /

1 row created.

SQL> INSERT INTO TEST5 VALUES ('a')
2 /

1 row created.

SQL> INSERT INTO TEST5 VALUES ('a')
2 /
INSERT INTO TEST5 VALUES ('a')
*
ERROR at line 1:
ORA-00001: unique constraint (SWPA.TEST5_U1) violated Received on Wed Jan 12 2005 - 11:42:04 CST