PHP怎么执行有带分号的MYSQL语句?

PHP怎么执行有带分号的MYSQL语句?

我想要搞一个排名的字段. 

SET @mycnt =0;  
SELECT (@mycnt := @mycnt +1) AS rankings,uid,sum(mark) AS marks FROM bo_log GROUP BY uid ORDER BY marks DESC


但是这样的话再MYSQL里面可以执行. 但是在PHP里的mysql_query就不能用了.. 如果把分号去掉在MYSQL里面不能用了rankings会变成空值

大神呢``