如何对不同的行求和？

如果您只想要一个总体数字，请尝试

select sum(PopEstimate2005), sum(Estimatesbase2000)from(    SELECt  Distinct        Zippres.CountyID,         us_co_est2005_allData.PopEstimate2005,         us_co_est2005_allData.Estimatesbase2000,         users_link_territory.userID     FROM         Zippres Inner Join         Users_link_territory ON zippres.CountyID = Users_link_territory.CountyID Inner Join         us_co_est2005_alldata ON zippres.FIPS = us_co_est2005_alldata.State AND zippres.pre = us_co_est2005_alldata.County     WHERe         (users_link_territory.userid = 4)) as foo