performance comparison: DISTINCT and GROUP BY

From: Devrim GUNDUZ <devrim(at)oper(dot)metu(dot)edu(dot)tr>
To: PostgreSQL Mailing Lists-SQL <pgsql-sql(at)postgresql(dot)org>
Subject: performance comparison: DISTINCT and GROUP BY
Date: 2002-08-19 11:22:08
Message-ID: Pine.LNX.4.44.0208191340200.4893-100000@oper.metu.edu.tr
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Hi,

We have two different queries:

SELECT name,surname FROM my_table GROUP BY name;

and

SELECT DISTINCT on(name) name,surname * FROM my_table;

which gives us the same result.

Do these queries differ by their performances? I mean, which one works
faster? DISTINCT or GROUP BY?

Best regards.

--

Devrim GUNDUZ

devrim(at)oper(dot)metu(dot)edu(dot)tr Tel : (312) 295 9318
devrim(dot)gunduz(at)linux(dot)org(dot)tr Faks : (312) 295 9494

Web : http://devrim.oper.metu.edu.tr
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