SQL> --Unique Key
SQL>
SQL>
SQL> create table myTable (
2 a number unique,
3 b number
4 );
Table created.
SQL>
SQL>
SQL> alter table myTable add constraint uq_ri_b unique (b);
Table altered.
SQL>
SQL>
SQL> insert into myTable values (4, 5);
1 row created.
SQL> insert into myTable values (2, 1);
1 row created.
SQL> insert into myTable values (2, 1); -- Dup
2 insert into myTable values (9, 8);
insert into myTable values (2, 1); -- Dup
*
ERROR at line 1:
ORA-00911: invalid character
SQL> insert into myTable values (6, 9);
1 row created.
SQL> insert into myTable values (null,9);
insert into myTable values (null,9)
*
ERROR at line 1:
ORA-00001: unique constraint (SYS.UQ_RI_B) violated
SQL> insert into myTable values (null,9);
insert into myTable values (null,9)
*
ERROR at line 1:
ORA-00001: unique constraint (SYS.UQ_RI_B) violated
SQL>
SQL> select * from myTable;
A B
---------- ----------
4 5
2 1
6 9
SQL>
SQL> drop table myTable;
Table dropped.
SQL>
SQL>