From: Volkan YAZICI <volkan.yazici@gmail.com>
To: pgsql-sql@postgresql.org
Subject: Combining two SELECTs by same filters
Date: Wed, 26 Oct 2005 18:16:13 +0300
Message-ID: <7104a7370510260816l9262d19j808d23c023e8445e@mail.gmail.com> (raw)
Hi,
I've a table like:
=> SELECT dt FROM sales WHERE id = 2;
dt
----------------------------
2005-10-25 21:43:35.870049
2005-10-25 21:43:36.254122
2005-10-25 21:43:36.591196
2005-10-25 21:43:36.893331
2005-10-25 21:43:37.265671
2005-10-25 21:43:37.688186
2005-10-25 22:25:35.213171
2005-10-25 22:25:36.32235
(8 rows)
And I want to collect the count of sales at hour = 21 and hour = 22.
For this purpose, I'm using below SELECT query:
=> SELECT
-> (SELECT count(id) FROM sales
-> WHERE id = 2
-> AND date_trunc('hour', dt) = '2005-10-25 21:00:00'),
-> (SELECT count(id) FROM sales
-> WHERE id = 2
-> AND date_trunc('hour', dt) = '2005-10-25 22:00:00');
?column? | ?column?
----------+----------
6 | 2
(1 row)
Isn't it possible to combine these two SELECTs as one. Because one of
their filters are same: id = 2. I'm just trying to avoid making 2
scans with nearly same filters.
Regards.
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To: pgsql-sql@postgresql.org
Cc: volkan.yazici@gmail.com
Subject: Re: Combining two SELECTs by same filters
In-Reply-To: <7104a7370510260816l9262d19j808d23c023e8445e@mail.gmail.com>
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