From: | Andreas Kretschmer <akretschmer(at)spamfence(dot)net> |
---|---|
To: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: There can be only one |
Date: | 2015-10-11 11:28:09 |
Message-ID: | 20151011112809.GA6083@tux |
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Thread: | |
Lists: | pgsql-general |
Andreas Kretschmer <andreas(at)a-kretschmer(dot)de> wrote:
> Create a partial unique index on is_default.
as an example:
test=# CREATE TABLE payment_via (
id int PRIMARY KEY,
provider text NOT NULL,
keys hstore NOT NULL DEFAULT '',
is_default boolean NOT NULL DEFAULT FALSE
);
CREATE TABLE
test=*# create unique index idx_default on payment_via(is_default) where
is_default;
CREATE INDEX
test=*# insert into payment_via values (1, 'foo','', true);
INSERT 0 1
test=*# insert into payment_via values (2, 'bla','', false);
INSERT 0 1
test=*# insert into payment_via values (3, 'blubb','', true);
ERROR: duplicate key value violates unique constraint "idx_default"
DETAIL: Key (is_default)=(t) already exists.
test=*#
Andreas
--
Really, I'm not out to destroy Microsoft. That will just be a completely
unintentional side effect. (Linus Torvalds)
"If I was god, I would recompile penguin with --enable-fly." (unknown)
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