Re: about select use random - Mailing list pgsql-admin

wangqi <wangqi@edgesoft.cn> writes:
> ��SQL-3
> select * from wk_mclid1 where id1= (round((random() * (10-1))::integer)
> + 1)::integer;

> When we excute SQL-3,sometimes the result was 0 record or more than 1
> record.

> Why?

random() is re-evaluated for each row scanned by the SELECT.

If you don't want that, you can use a WITH to lock down the result of a
single random() call.

            regards, tom lane