Oracle Database SQL — Question 262

Which three are true about scalar subquery expressions? (Choose three.)

Answer options

• A. They can be nested.
• B. They cannot be used in the VALUES clause of an INSERT statement.
• C. A scalar subquery expression that returns zero rows evaluates to zero.
• D. They can be used as default values for columns in a CREATE TABLE statement.
• E. A scalar subquery expression that returns zero rows evaluates to NULL.
• F. They cannot be used in GROUP BY clauses.

Correct answer: A, E, F

Explanation

The correct answers A, E, and F highlight the properties of scalar subqueries: they can indeed be nested, return NULL when no rows are found, and cannot be used in GROUP BY clauses. Option B is incorrect because scalar subqueries can be used in the VALUES clause, while option C is wrong since a scalar subquery that returns zero rows evaluates to NULL, not zero. Option D is also incorrect because scalar subqueries cannot be used as default values in CREATE TABLE statements.