agora inbox for pgsql-sql@postgresql.org  

help / color / mirror / Atom feed

From: Harald Fuchs <hari.fuchs@gmail.com>
To: pgsql-sql@postgresql.org
Subject: Re: Display group title only at the first record within each group
Date: Wed, 24 Aug 2016 10:03:27 +0200
Message-ID: <87d1ky1tm8.fsf@hf.protecting.net> (raw)
References: <1471968815.2343352.703756417.6A1C9C13@webmail.messagingengine.com>
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-sql>

CN <cnliou9@fastmail.fm> writes:

> Hi!
>
> Such layout is commonly seen on real world reports where duplicated
> group titles are discarded except for the first one.
>
> CREATE TABLE x(name TEXT,dt DATE,amount INTEGER);
>
> COPY x FROM stdin;
> john    2016-8-20       80
> mary    2016-8-17       20
> john    2016-7-8        30
> john    2016-8-19       40
> mary    2016-8-17       30
> john    2016-7-8        50
> \.
>
> My desired result follows:
>
> john    2016-07-08      50
> 					30
> 		2016-08-19      40
> 		2016-08-20      80
> mary    2016-08-17      20
> 					30

Use window functions:

SELECT CASE
       WHEN lag(name) OVER (PARTITION BY name ORDER BY name, dt) IS NULL
       THEN name
       ELSE NULL
       END,
       CASE
       WHEN lag(dt) OVER (PARTITION BY name, dt ORDER BY name, dt) IS NULL
       THEN dt
       ELSE NULL
       END,
       amount
FROM x
ORDER BY name, dt



-- 
Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-sql

view thread (2+ messages)

Message-ID: <87d1ky1tm8.fsf@hf.protecting.net>
Permalink:  ../87d1ky1tm8.fsf@hf.protecting.net/
Also on:    postgresql.org/message-id/87d1ky1tm8.fsf@hf.protecting.net

reply

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: hari.fuchs@gmail.com
  Subject: Re: Display group title only at the first record within each group
  In-Reply-To: <87d1ky1tm8.fsf@hf.protecting.net>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox