Re: Random()

am Sat, dem 18.11.2006, um 23:02:33 +0530 mailte Rajesh Kumar Mallah folgendes:
> >select <bigint_column> from <your_table> order by random() limit 1;
>
> This query will tend to get slower as the table grows because of the
> sorting.

Right.

>
> it possible to get a row from a random offset
> how about
>
> select <bigint_column> from <your_table> limit 1 offset 20000*random() ;

For instance, you have a table with only 500 rows and random() returns
0.999? In other words: in think, this is a bad idea, unless you use a
constant for the offset-calculation thats not larger than the number of
rows in this table. For this, you need this value, but select count(1)
from table force a seqscan -> slow.

Andreas
--
Andreas Kretschmer
Kontakt: Heynitz: 035242/47215, D1: 0160/7141639 (mehr: -> Header)
GnuPG-ID: 0x3FFF606C, privat 0x7F4584DA http://wwwkeys.de.pgp.net