On 7/13/06, Chris Hoover <revoohc@gmail.com> wrote:
> On this table, I have created a unique index on payer_trn03, payer_trn04,
> and expire_timestamp. However, since the expire_timestamp is normally null,
> the unique index does not appear to be working. I have been able to enter
> two identical rows into this table.
>
> Why is PostgreSQL not enforcing this index? This appears to be a pretty
> major a bug? It would seem that you could have a unique index across
> columns that might have a null in them.
From:
http://www.postgresql.org/docs/8.1/interactive/indexes-unique.html
Quote:
"When an index is declared unique, multiple table rows with equal
indexed values will not be allowed. Null values are not considered
equal. A multicolumn unique index will only reject cases where all of
the indexed columns are equal in two rows."
Regards,
Rodrigo
