Re: unique constraint definition within create table
От | David G. Johnston |
---|---|
Тема | Re: unique constraint definition within create table |
Дата | |
Msg-id | CAKFQuwZeW5W9JuigEOo9ouxPvm_4bZbufbDpmLg=L+gLSw-0bA@mail.gmail.com обсуждение исходный текст |
Ответ на | unique constraint definition within create table (Andreas Kretschmer <akretschmer@spamfence.net>) |
Список | pgsql-sql |
Hi @ll,
i'm trying to create a table with 2 int-columns and a constraint that a
pair of (x,y) cannot be as (y,x) inserted:
test=# create table foo(u1 int,u2 int, unique (least(u1,u2),greatest(u1,u2)));
ERROR: syntax error at or near "("
LINE 1: create table foo(u1 int,u2 int, unique (least(u1,u2),greates...
I know, i can solve that in this way:
test=*# create table foo(u1 int,u2 int);
CREATE TABLE
test=*# create unique index idx_foo on foo(least(u1,u2),greatest(u1,u2));
CREATE INDEX
But is there a way to define the unique constraint within the create table - command?
You might consider adding a table constraint "u1 <= u2". You could also consider adding a trigger that munges data on INSERT/UPDATE so that this constraint is met regardless of the order supplied by the user.
David J.
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