From: | Joe Conway <mail(at)joeconway(dot)com> |
---|---|
To: | "Thomas T(dot) Thai" <tom(at)minnesota(dot)com> |
Cc: | PostgreSQL General <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: ALTER TABLE & NOT NULL |
Date: | 2002-04-06 21:30:35 |
Message-ID: | 3CAF68FB.2030802@joeconway.com |
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Lists: | pgsql-general |
Thomas T. Thai wrote:
>>>
>>
>>I think you have to add a table constraint to do that. Something like:
>>
>>ALTER TABLE auth_users ADD CONSTRAINT auth_users_email CHECK (email is
>>not null);
>
>
> is this also what happens at the time of table creation when one specifies
> that a column is to be NOT NULL?
Not quite the same, but the net effect is. To illustrate, I created 2
tables foobar1 and foobar2. foobar2 had the constraint added after
creation, foobar1 was created with the f1 column set to not null. Here's
what it looks like from psql:
test=# \d foobar1
Table "foobar1"
Column | Type | Modifiers
--------+---------+-----------
f1 | integer | not null
test=# \d foobar2
Table "foobar2"
Column | Type | Modifiers
--------+---------+-----------
f1 | integer |
Check constraints: "foobar2_f1" (f1 IS NOT NULL)
I think I remember some discussion around making a way to add a not null
modifier, but I don't believe it can be done today. Hopefully someone
will correct me if I'm wrong here.
(Except, maybe by hacking the system tables directly - it seems to work
for me, but that's always a risky proposition. Make sure you update the
field first to fill in any NULLs with some default value, or you won't
be able to UPDATE those rows afterward).
Joe
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