Which two statements are true regarding subqueries?

Which two statements are true regarding subqueries? (Choose two.)

A.
The ORDER BY clause can be used in the subquery.

B.
A subquery can be used in the FROM clause of a SELECT statement.

C.
If the subquery returns NULL, the main query may still return result rows.

D.
A subquery can be placed in a WHERE clause, GROUP BY clause, or a HAVING clause.

E.
Logical operators, such as AND, OR and NOT, cannot be used in the WHERE clause
of a subquery.

Leave a Reply 4

bogdan

ABC is correct:

select count(*) result from (select * from dual where 2 + 2 = 5 order by 1);

select nvl((select dummy from dual where 2 + 2 = 5), ‘C is correct’) result from dual;

select ‘C is correct’ result from dual where ((select dummy from dual where 2 + 2 = 5) is null);

RESULT
———-
0

RESULT
————
C is correct

dames

If the subquery returns NULL, the main query returns ZERO rows.
This is exactly what count(*) in your example shows.

bogdan

C is correct

Hao

c is incorrect
bogdan’s 3rd example is wrong because his sub-query is like (null is null)