From: Rod Taylor <pg@rbt.ca>
To: Ying Lu <ying_lu@cs.concordia.ca>
Cc: pgsql-sql@postgresql.org
Subject: Re: About "Alter table... alter column.. TYPE ... "
Date: Mon, 18 Apr 2005 17:09:46 -0400
Message-ID: <1113858586.3859.526.camel@home> (raw)
In-Reply-To: <42641AD9.60708@cs.concordia.ca>
References: <42641AD9.60708@cs.concordia.ca>
> To alter table column from varchar(32) to date. "Alter table" command
> does not seem to work:
>
> alter table test alter column col type date ;
> ERROR: column "col1" cannot be cast to type "date"
Alter table will not automatically throw away information. That is, in
cases where it believes you may lose data, it will not perform it.
That said, you can coax it into doing so.
ALTER TABLE test ALTER COLUMN col TYPE date USING CAST(col AS date);
USING is an arbitrary expression capable of doing most things you can do
in an UPDATE.
--
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To: pgsql-sql@postgresql.org
Cc: pg@rbt.ca, ying_lu@cs.concordia.ca
Subject: Re: About "Alter table... alter column.. TYPE ... "
In-Reply-To: <1113858586.3859.526.camel@home>
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