Re: Random row SELECT der auf ggf. fehlende IDīs achtet

[Jens Peter Möller <jpmnet_(at)_gmx.net>]

----- Original Message -----
From: "Tobias Orterer" <der_(at)_Tobi.li>
To: <mysql-de_(at)_lists.4t2.com>
Sent: Friday, January 12, 2001 1:46 PM
Subject: Random row SELECT der auf ggf. fehlende IDīs achtet


> einem SELECT. Hab schon limit rand(),1; ausprobiert weil das
> "angeblich" gehen sollte, war aber nicht der fall...
>

Ok, ich war etwas voreilig und habe Dein Posting nicht
zuende gelesen.
Also schnell mal
http://www.mysql.com/doc/M/a/Mathematical_functions.html besucht.

---------------------------------------------
RAND(N)
Returns a random floating-point value in the range 0 to 1.0. If an integer
argument N is specified, it is used as the seed value:
mysql> select RAND();
        -> 0.5925
mysql> select RAND(20);
        -> 0.1811
mysql> select RAND(20);
        -> 0.1811
mysql> select RAND();
        -> 0.2079
mysql> select RAND();
        -> 0.7888

You can't use a column with RAND() values in an ORDER BY clause, because
ORDER BY would evaluate the column multiple times. In MySQL Version 3.23,
you can, however, do: SELECT * FROM table_name ORDER BY RAND() This is
useful to get a random sample of a set SELECT * FROM table1,table2 WHERE a=b
AND c<d ORDER BY RAND() LIMIT 1000. Note that a RAND() in a WHERE clause
will be re-evaluated every time the WHERE is executed.
-----------------------------------------------

Dann müßte ja eigentlich folgendes gehen:

select irgendwas from tabelle order by rand() limit 1


Gruß,
Jens Peter Möller


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