用SQL查询毛利率，毛利率=售价-进价/售价

现有语句如下如何在这条语句里实现查询毛利率的功能
select bmbm,spbm,sum(xssl) from t_xsmx where xsjg<=hsjg and xsrq>='20120201' and xsrq<='20120219' group by bmbm,spbm
/

select bmbm,spbm,xssl,(bmbm-spbm)/bmbm as 毛利率 from
(
select bmbm,spbm,sum(xssl) as xssl from t_xsmx where xsjg<=hsjg and xsrq>='20120201' and xsrq<='20120219' group by bmbm,spbm
)w

不知道哪个是哪个字段,就差不多的写了一下,请参考

我不会~~~但还是要微笑~~~：）