一个数据库面试题，有点懵了，求救

鸣人吃土豆

如上图，这几题咋做呢？

fangsh111

1、select * from (select * from jufei wehrfe a 51<= expenses<100 and month in (201006,201007,201008) ) t1 ,
(select * from jufei where expenses=0 and  month in  (201006 ,201007) ) t2 where t1.msisdn=t2.msisdn  ;

2、select * fron jifei wehre moutn  between 201001 and 201010 and substr(msisdn,-4) in (1133,4646,9999);

4、select discont(*) from jifei where  substr(mount,-2) in (09,10) and expenses > 30;