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* performance comparison: DISTINCT and GROUP BY
@ 2002-08-19 11:22 Devrim GUNDUZ <devrim@oper.metu.edu.tr>
2002-08-19 12:26 ` Re: performance comparison: DISTINCT and GROUP BY Christopher Kings-Lynne <chriskl@familyhealth.com.au>
0 siblings, 1 reply; 2+ messages in thread
From: Devrim GUNDUZ @ 2002-08-19 11:22 UTC (permalink / raw)
To: pgsql-sql
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@oper.metu.edu.tr Tel : (312) 295 9318
devrim.gunduz@linux.org.tr Faks : (312) 295 9494
Web : http://devrim.oper.metu.edu.tr
-------------------------------------
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: performance comparison: DISTINCT and GROUP BY
2002-08-19 11:22 performance comparison: DISTINCT and GROUP BY Devrim GUNDUZ <devrim@oper.metu.edu.tr>
@ 2002-08-19 12:26 ` Christopher Kings-Lynne <chriskl@familyhealth.com.au>
0 siblings, 0 replies; 2+ messages in thread
From: Christopher Kings-Lynne @ 2002-08-19 12:26 UTC (permalink / raw)
To: Devrim GUNDUZ <devrim@oper.metu.edu.tr>; pgsql-sql
Hi Devrim,
You can use the EXPLAIN ANALYZE syntax to find out quite easily.
Chris
----- Original Message -----
From: "Devrim GUNDUZ" <devrim@oper.metu.edu.tr>
To: "PostgreSQL Mailing Lists-SQL" <pgsql-sql@postgresql.org>
Sent: Monday, August 19, 2002 7:22 PM
Subject: [SQL] performance comparison: DISTINCT and GROUP BY
>
> 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@oper.metu.edu.tr Tel : (312) 295 9318
> devrim.gunduz@linux.org.tr Faks : (312) 295 9494
>
> Web : http://devrim.oper.metu.edu.tr
> -------------------------------------
>
>
> ---------------------------(end of broadcast)---------------------------
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>
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2002-08-19 11:22 performance comparison: DISTINCT and GROUP BY Devrim GUNDUZ <devrim@oper.metu.edu.tr>
2002-08-19 12:26 ` Christopher Kings-Lynne <chriskl@familyhealth.com.au>
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