mysql中給查詢出的結果集添加自增序號

select (@i:=@i+1) i,emp.* from emp,(select @i:=0) it

 

按部門分組並按薪資總和從大到小排序求薪資總和第二高的部門名稱和薪資總和：select c.ename,c.s from (select (@i:=@i+1) i,e.*  from (SELECT ename,SUM(sal) s FROM emp GROUP BY deptno ORDER BY s desc) e,(select @i:=0) it) c where c.i=2