Ruben Blanco wrote on 08.03.2011 00:30:
Hi:
Is there anyway to create a unique index or constraint on part of a column?
Something like this, but something that works ;-)
ALTER TABLE invoices
ADD CONSTRAINT cons UNIQUE (EXTRACT(YEAR FROM invoice_date),
innvoice_number);
Thanks for any help.
Ruben,
CREATE UNIQUE INDEX idx_cons ON invoices (EXTRACT(YEAR FROM invoice_date),
innvoice_number);
The only difference to a unique constraint is, that it cannot be used as the
target of a foreign key constraint.
Regards
Thomas
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