随機取mysql的資料

看了部落格http://dditblog.com/itshare_192.html

記錄下：

SELECT * FROM xc_optional_group_items AS r1 JOIN

(SELECT ROUND(RAND() * (SELECT MAX(id) FROM xc_optional_group_items)) AS id) AS r2

WHERE r1.id >= r2.id

ORDER BY r1.id ASC

LIMIT 2;