From: A. Kretschmer <andreas.kretschmer@schollglas.com>
To: pgsql-sql@postgresql.org
Subject: Re: Using || operator to fold multiple columns into one
Date: Wed, 23 Dec 2009 09:50:31 +0100
Message-ID: <20091223085031.GA12007@a-kretschmer.de> (raw)
In-Reply-To: <4B31D619.1090706@obviously.com>
References: <4B31D619.1090706@obviously.com>
In response to Bryce Nesbitt :
> Dear experts,
>
> This point is confusing me with the || operator. I've got a table with
> "one column per data type", like so:
>
> # \d context_keyvals;
> Table "public.context_keyvals"
> Column | Type | Modifiers
> -------------+-----------------------------+-----------
> context_key | integer | not null
> keyname | text |
> t_number | integer |
> t_string | text |
> t_boolean | boolean |
> t_date | timestamp without time zone |
> Indexes:
> "context_keyvals_ck" btree (context_key) CLUSTER
> Foreign-key constraints:
> "context_keyvals_context_key_fkey" FOREIGN KEY (context_key)
> REFERENCES contexts(context_key) ON DELETE CASCADE
> # select version()
> PostgreSQL 8.3.8 on x86_64-pc-linux-gnu, compiled by GCC gcc-4.3.real
> (Debian 4.3.2-1.1) 4.3.2
>
> ------------------------------
> Just for pretty sake I'd like to be able to use psql to view it like this:
>
> # select context_key,keyname,t_number||t_string||t_date||t_boolean as
> value from context_keyvals;
>
> But it is not working, the columns always come up empty. I can use the
> || operator to concatenate strings:
> # select '--'||t_number::text from context_keyvals;
>
> But the moment I try to combine columns, the result is blank.
> # select '--'||t_number::text||t_string::text from context_keyvals;
At least one column contains NULL. To handle that, use
coalesce(column,'') to change NULL to ''.
Andreas
--
Andreas Kretschmer
Kontakt: Heynitz: 035242/47150, D1: 0160/7141639 (mehr: -> Header)
GnuPG: 0x31720C99, 1006 CCB4 A326 1D42 6431 2EB0 389D 1DC2 3172 0C99
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-sql@postgresql.org
Cc: andreas.kretschmer@schollglas.com
Subject: Re: Using || operator to fold multiple columns into one
In-Reply-To: <20091223085031.GA12007@a-kretschmer.de>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox