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Create unique index or constraint on part of a column - Mailing list pgsql-general

From Ruben Blanco
Subject Create unique index or constraint on part of a column
Date
Msg-id AANLkTinhtA7Gy4LrH16aMz=kPevyPXNx8-d355gV=g84@mail.gmail.com
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Responses Re: Create unique index or constraint on part of a column  (Thomas Kellerer <spam_eater@gmx.net>)
Re: Create unique index or constraint on part of a column  (Jeff Davis <pgsql@j-davis.com>)
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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,

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