简单的SQL查询

Question

我有3个表如下.

salesman(sid,sname)
location(lid,lname)
sales_loc(sid,lid)

现在我要打印已经访问过所有地点的销售员的sid和sname.我想要一个SQL查询,我不想要PL/SQL代码.

Answer 1

select sid, sname from salesman
where not exists 
        (select 1 from location
          where not exists
                  (select 1 from sales_loc
                    where sid=saleman.sid 
                     and lid = location.lid));