Re: How can unique columns being case-insensitive be accomplished?

On Mon, Sep 16, 2002 at 09:38:46AM -0400, Tom Lane wrote:
> "Jrg" <mail2holly(at)gmx(dot)de> writes:
> > How can this problem be overcome? Any ideas?
>
> Create a unique index on lower(name).

I'm sure Jrg can follow this tip, but for the archives, I'll include
the full syntax:

CREATE UNIQUE INDEX drug_lwr_idx ON drug ( lower(name) )

Another trick would be to use your trigger to lower() the inserted/updated
names, rather than only as a test, combined with a regular unique index:

CREATE FUNCTION lower_drug () RETURNS OPAQUE AS '
BEGIN
NEW.name = lower(NEW.name);
RETURN NEW;
END;
' LANGUAGE 'plpgsql';

CREATE TRIGGER drug_insert BEFORE UPDATE OR INSERT ON drug
FOR EACH ROW EXECUTE PROCEDURE lower_drug();

That keeps your data nice and clean and consistent, otherwise
the first time a MixedCaseDrugName goes in, it'll keep the correct
'mixedcasedrugname' from being inserted, later. Be very sure that lower()
gives you exactly the output you want, however.

Ross