On Aug 15, 2008, at 12:35 PM, William Garrison wrote:
Is there an easy way to write one single query that can alternate between ASC and DESC orders? Ex:CREATE OR REPLACE FUNCTION GetSomeStuff(_start integer, _count integer, _sortDesc boolean)RETURNS SETOF text AS $BODY$ SELECT something FROM whatever WHERE whatever ORDER BY another_column OFFSET $1 LIMIT $2 ($4 = true ? 'DESC' : 'ASC'); $BODY$ LANGUAGE 'sql' VOLATILE; I can think of a few ways, but I am hoping for something more elegant.1) In my case another_column is numeric, so I could multiple by negative one if I want it in the other order. Not sure what this does to the optimizer if the column is indexed or not.
In my experience, it's pretty rare for an index to be used to satisfy an ORDER BY.
2) I could write the statement twice, once with ASC and once with DESC, and then use IF/ELSE structure to pick one.3) I could generate the statement dynamically.I am hoping there is some super secret extension that can handle this. This seems like one of those foolish things in SQL, where it is too declarative. ASC and DESC should be parameters to order by, not a part of the syntax. But I digress... any other suggestions?
None that I can think of, unfortunately. It might not be horribly hard to allow plpgsql to use a variable for ASC vs DESC; that might be your best bet.
-- Decibel!, aka Jim C. Nasby, Database Architect decibel@xxxxxxxxxxx Give your computer some brain candy! www.distributed.net Team #1828
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