WITHIN GROUP ORDER BY RAND() fails

I like to order by random within my group.

→ WITHIN GROUP ORDER BY RAND()

but it gives me

Errormessage: sphinxql: syntax error, unexpected ‘(’, expecting $end near '()

Does this simply not work, or is the syntax incorrect?

you need to move expression into select list then use alias to that expression at group by

thx, this works!

SELECT RAND() AS rand… GROUP BY … WITHIN GROUP ORDER BY rand DESC