Re: Changing a table column datatype

Hi Marshall,

based on the error msg your getting back from postgres, your column
fqdn is set to 'not null'. therefore you must enter something into
that field when trying to insert a new record.

going off your example, you could do it like this:

insert into mytable (fqdn, mycol_new) select fqdn, mycol from mytable;


----- Original Message -----
From: <marshall@perilith.com>
Date: Mon, 12 May 2003 20:18:57 -0400 (EDT)
To: <pgsql-novice@postgresql.org>
Subject: [NOVICE] Changing a table column datatype

> Hello,
>
> This has been asked before, but the responses weren't clear enough
> for me to understand.
>
> I have a table `mytable' with an attribute `mycol' of datatype char(4) and
> I'd like to change it to varchar(20).  Mycol is populated by two values -
> NULLs and four element chars.  What I've tried thusfar:
>
>  db=> ALTER TABLE mytable ADD COLUMN mycol_new VARCHAR(20);
>  ALTER TABLE
>  db=> INSERT INTO mytable (mycol_new) SELECT mycol FROM mytable;
>  ERROR:  ExecInsert: Fail to add null value in not null attribute fqdn
>
> The `fqdn' attribute is another column in mytable.
>
> So is it the case that INSERT doesn't like inserting NULL values?  Is
> there another way to do this?
>
> I'm using PostgreSQL 7.3.2.
>
> TIA!
>
> -mt
>
>
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