Re: UNIQUE KEY with null value...

http://www.postgresql.org/docs/8.0/interactive/sql-createtable.html

For the purpose of a unique constraint, null values are not considered
equal.

On Tue, Nov 01, 2005 at 03:09:24PM -0300, Diego wrote:
> Hi,
> I?m a brazilian programmer!
>
> I have a question about Postgres UNIQUE KEY. Look:
>
> (Step 1)
> CREATE TABLE test (
> id integer not null primary key,
> id_uni integer not null,
> cod integer,
> name varchar(40),
> constraint test_uk unique(id_uni, cod)
> )
>
> (Step 2)
> insert into test (id, id_uni, cod, name)
> values (1, 1, null, 'A')
>
> (Step 3)
> insert into test (id, id_uni, cod, name)
> values (2, 1, null, 'B') =========> [Have the same UNIQUE KEY]
>
> Why postgresql don?t break insertion in this case????
>
> Thanks
> Diego Ziquinatti
> Brazil
>
>
>
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