修改後的SQL，可應用與RFM分析

 1.分組查詢，得到的是按科目分 SELECT  a.sname,a.sno,a.score,  IF( @className = a.project_name,@rank := @rank + 1,@rank :=1 ) AS rank, (@className := a.project_name) project_name           FROM student23   a, ( sel

>>阅读原文<<