mysql查询获取排名sql语句

FROM 
 ( 
     SELECT A.*,@rank:=@rank+1 as pm 
     FROM    
     (   
      SELECT banji,avg(score) as AvgS FROM table_test GROUP BY banji  ORDER BY AvgS   DESC   
     ) A ,(SELECT @rank:=0) B  
 ) M 
 ORDER BY M.banji