Hi,
Try to use a calculated index:
(tested similar solution, but not this code)
CREATE OR REPLACE FUNCTION TestOrder (nameTable.weekDay%TYPE) RETURNS INT AS
'
DECLARE
numWeekDay INT;
BEGIN
if ($1 = ''Wed'') then numWeekDay := 1;
if ($1 = ''Tue'') then numWeekDay := 2;
.....
RETURN (numWeekDay);
END;
' LANGUAGE 'plpgsql' STRICT IMMUTABLE;
CREATE INDEX idx_TestOrder
ON nameTable USING btree (TestOrder(nameTable.weekDay));
SELECT * FROM trajecte ORDER BY TestOrder(nameTable.weekDay);
Regards
----- Original Message -----
From: "Joseph Shraibman" <jks@selectacast.net>
To: <pgsql-sql@postgresql.org>
Sent: Wednesday, January 25, 2006 2:23 AM
Subject: [SQL] sorting by day of the week
p8:owl=>SELECT to_char( logtime, 'Dy'),count(*) FROM logtab WHERE
date_trunc('day', logtime) > current_date + '7 day ago'::interval group by
to_char( logtime, 'Dy') ORDER BY to_char( logtime, 'Dy') DESC;
to_char | count
---------+-------
Wed | 1447
Tue | 618
Thu | 1161
Sun | 230
Sat | 362
Mon | 760
Fri | 1281
(7 rows)
The problem is that I want those results sorted in day of week order, not
text order of the day name, so I tried this:
p8:owl=>SELECT to_char( logtime, 'Dy'),count(*) FROM sclog WHERE
date_trunc('day', logtime) > current_date + '7 day ago'::interval group by
to_char( logtime, 'Dy') ORDER BY to_char( logtime, 'D') DESC;
ERROR: column "sclog.logtime" must appear in the GROUP BY clause or be
used in an aggregate function
Now obviously I don't want to group by logtime (a timestamp) so how do I
work around this? What I really need is a function that converts from the
char representation to a day of week number or vice versa. I also have
the same problem with month names.
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