按某个字段分组并排序后，取每一组的第一条数据

select * from(
select
a.TEMPLATEID,ROW_NUMBER()OVER(PARTITION BY a.TEMPLATEID ORDER BY b.STEPNO DESC ) ROWNO,b.ROLEID,A.BUSINESSID
from FHC_JW.WF_BUSINESSFLOWRELATION a,FHC_JW.WF_FLOWTEMPLATEDETAIL b
where a.TEMPLATEID = b.TEMPLATEID
) where ROWNO=1

语法：ROW_NUMBER()OVER(PARTITION BY 分组字段 ORDER BY 排序字段 DESC )