From: Tom Lane <tgl@sss.pgh.pa.us>
To: Reza Shanbehbazari Mirzaei <mirzaei@stud.ntnu.no>
Cc: pgsql-sql@postgresql.org
Subject: Re: User defined types
Date: Thu, 25 Nov 2004 13:29:42 -0500
Message-ID: <1114.1101407382@sss.pgh.pa.us> (raw)
In-Reply-To: <Pine.LNX.4.58.0411201729220.32082@jaguar.stud.ntnu.no>
References: <Pine.LNX.4.58.0411201729220.32082@jaguar.stud.ntnu.no>
Reza Shanbehbazari Mirzaei <mirzaei@stud.ntnu.no> writes:
> I have a user define type called VALID_TIME. It is declared as follows:
> CREATE TYPE VALID_TIME AS (t_s TIMESTAMP, t_e TIMESTAMP);
> Once I have used this in a table declaration, is it possible to extract
> parts of it, for example to only read t_s or t_e? If so, how do I do this?
8.0 supports using composite types as table columns, but prior versions
don't really. In 8.0 you'd do something like
create table myt (vt valid_time);
select (vt).t_s from myt;
or
select (myt.vt).t_s from myt;
The parentheses are essential --- without them, you'd have for instance
select vt.t_s from myt;
which looks like a reference to field t_s of table vt, not what you
want.
You can hack around the problem in earlier versions by creating helper
functions, eg
select get_t_s(vt) from myt;
but it's ugly enough to make one wonder why bother with a composite type.
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, mirzaei@stud.ntnu.no
Subject: Re: User defined types
In-Reply-To: <1114.1101407382@sss.pgh.pa.us>
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