把数据汇总后进行排行，在后面加一列排行榜，用的这个变量赋值，但是一直报错，是不是这个用法有什么限制，大佬们，你们看一下
select y5.FDESCRIPTION as 子公司, sum(cast(y2.FNOTAXAMOUNT as decimal(16,2))) as 销售收入,
sum(cast(y6.FREALQTY as decimal(16,0))) as 车辆销售数量,
sum(cast(y2.FNOTAXAMOUNT as decimal(16,2))-isnull(cast(y4.FCOSTAMOUNT_LC as decimal(16,2)),0)) as 毛利,
@r:=@r+1 as rank
from t_AR_receivable y1
left join t_AR_receivableEntry y2 on y1.FID=Y2.fid
left join T_SAL_OUTSTOCK y3 on y2.FSOURCEBILLNO=y3.FBILLNO
left join T_SAL_OUTSTOCKENTRY_F y4 on y3.FID =y4.fid
left join T_ORG_ORGANIZATIONS_L y5 on y1.FSETTLEORGID=y5.FORGID
left join T_SAL_OUTSTOCKENTRY y6 on y3.FID =y6.fid
left join T_BD_MATERIAL y7 on y2.FMATERIALID=y7.FMATERIALID
group by y5.FDESCRIPTION
--order by sum(cast(y2.FNOTAXAMOUNT as decimal(16,2))) desc,select (@r:=0) r