Oracle SQL Oracle SQL Joins and Subqueries 3

Question 1

What is the difference between IN and EXISTS in Oracle SQL for subqueries?

Accepted Answer

EXISTS stops at first match (short-circuit), IN evaluates all subquery rows

Answer

IN uses indexes, EXISTS does not

Answer

EXISTS returns values, IN returns TRUE/FALSE only

Answer

There is no functional difference

Question 2

In Oracle SQL, which join returns all rows from both tables, with NULLs where there is no match?

Accepted Answer

FULL OUTER JOIN

Answer

INNER JOIN

Answer

LEFT OUTER JOIN

Answer

CROSS JOIN

Question 3

What does NOT EXISTS return if the subquery finds no matching rows in Oracle SQL?

Accepted Answer

TRUE

Answer

FALSE

Answer

NULL

Answer

An error

Question 4

Which Oracle SQL clause is used to specify the join condition in an ANSI-style join?

Accepted Answer

ON

Answer

USING

Answer

WHERE

Answer

JOIN CONDITION

Question 5

What happens if a scalar subquery returns more than one row in Oracle SQL?

Accepted Answer

Oracle raises ORA-01427 error

Answer

Oracle returns the first row automatically

Answer

Oracle returns NULL

Answer

Oracle returns all rows as a list

Question 6

Which Oracle SQL join type produces results equivalent to UNION of LEFT JOIN and RIGHT JOIN?

Accepted Answer

FULL OUTER JOIN

Answer

INNER JOIN

Answer

CROSS JOIN

Answer

SELF JOIN