Select count(1)     From eemployee     where status=1     and eid not in (select eid from CBENEFIT_STATUS)居然一条记录都没有？是因为select eid from CBENEFIT_STATUS 中eid为空解决方法：    1/ 改为select eid from CBENEFIT_STATUS where eid is not null    --  where eid is not null    Select count(1)         From eemployee         where status=1         and eid not in (select eid from CBENEFIT_STATUS where eid is not null)    2/ select * from table1 A where not exists (SELECT * FROM table2 B where B.col1=A.col1)     Select count(1)         From eemployee a        where status=1        and not exists (select 1 from CBENEFIT_STATUS b where a.eid = b.eid)参考网址:http://x-spirit.iteye.com/blog/615603