Last x records

From: "Matthias Teege" <matthias@mteege.de>

Moin,

is there any way to get the last x records of an query
result?

I can use "... order by x DESC LIMIT n" but I need ASC not
DESC, the last records in the correct order.

If you know how many records there are you could use "LIMIT n OFFSET m"
where m = number of records - n

Otherwise, the only thing that I can think of is to set up a view that does
the LIMIT n on a DESC then sort ASC when selecting on that view - might
work.

- Richard Huxton

"Richard Huxton" <dev@archonet.com> writes:

From: "Matthias Teege" <matthias@mteege.de>

is there any way to get the last x records of an query
result?

Otherwise, the only thing that I can think of is to set up a view that does
the LIMIT n on a DESC then sort ASC when selecting on that view - might
work.

Not in 7.0.* or before --- there is just plain no way to get multiple
levels of sorting in a query. In 7.1 you can do it like this:

SELECT * FROM
(SELECT ... ORDER BY foo DESC LIMIT n) ss
ORDER BY foo;

A workaround in 7.0.* is to use a temp table:

SELECT ... INTO TEMP t1 ... ORDER BY foo DESC LIMIT n;
SELECT * FROM t1 ORDER BY foo;
DROP TABLE t1;

The extra sort step shouldn't affect the speed much as long as n is small.

regards, tom lane