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constraints [message #9361]

Thu, 06 November 2003 00:50

lok
Messages: 4
Registered: November 2003

Junior Member

is UNIQUE is a constrints?

if so how can i alter table

SQL> desc station;
Name Null? Type
------------------------------- -------- ----
STATION NOT NULL VARCHAR2(20)
TWO_L VARCHAR2(2)
THREE_L NOT NULL VARCHAR2(3)

on the col station.

thanks for kond co-operation.

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Re: constraints [message #9365 is a reply to message #9361]

Thu, 06 November 2003 01:19

Maaher
Messages: 7065
Registered: December 2001

Senior Member

Yes it is a constraint type.

Again, an ALTER TABLE will help you out:

ALTER TABLE your_table ADD CONSTRAINT your_constraint_name UNIQUE(your_column);

Remember, the column should already contain unique values. If you want to create the constraint and you have duplicate values, you can add the 'DISABLE' keyword. That way, the constraint will be created but in a disabled state. Now you can modify the values until they are unique, and enable the constraint by...alter table your_table enable constraint constraint_name.

MHE

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