oracle, missing right parenthesis when adding subquery

Question

The inner query is as follow, which works fine independently

select graduate.univid
from graduate, projectmanager, university
where graduate.empid = projectmanager.mgrid and rownum = 1
group by graduate.univid
order by count(graduate.univid) desc;

but when put as subquery, ORACLE sqlplus keep giving "missing right parenthesis" error

select university.univname
from university
where exists 
(
select graduate.univid
from graduate, projectmanager, university
where graduate.empid = projectmanager.mgrid and rownum = 1
group by graduate.univid
order by count(graduate.univid)
);

I have checked similar questions on stackoverflow, but doesn't really help

Answer 1

you use exists so you have to give the condition of university and the subquery. you missed it you get the error i ll guess the right query:

select t1.univname
from university t1
where exists 
(  select 1 from (
   select graduate.univid
   from graduate, projectmanager, university
   where graduate.empid = projectmanager.mgrid and rownum = 1
   group by graduate.univid
   order by count(graduate.univid)) t2 where t2.univid = t1.univid
);

Answer 2

Assuming that rest of your logic is correct, the problem is order by clause. You should use it in subquery. 应该在子查询中使用它。 Try this

select university.univname
from university
where exists 
(
select graduate.univid
from graduate, projectmanager, university
where graduate.empid = projectmanager.mgrid and rownum = 1
group by graduate.univid
);

You can try it out yourself.

This query will return 1

select 1 from dual
where exists
(select 2 as id from dual)

But this will fail and give you ORA-00907: missing right parenthesis

select 1 from dual
where exists
(select 2 as id from dual order by id )