两种方法不同的效率！
方法1
select * from userinfo,achieveamount where userinfo.unionid = achieveamount.unionid(+) and achieveamount.unionid IS NULL
方法2
select * from userinfo where userinfo.unionid not in (select achieveamount.unionid from achieveamount)
我们要采用方法1这样性能要比2好很多！
