Oracle Database Administration I — Question 128

Which three statements are true regarding single row subqueries? (Choose three.)

Answer options

• A. A SQL statement may have multiple single row subquery blocks.
• B. They can be used in the WHERE clause.
• C. They must be placed on the left side of the comparison operator or condition.
• D. They can be used in the HAVING clause.
• E. They must be placed on the right side of the comparison operator or condition.
• F. They must return a row to prevent errors in the SQL statement.

Correct answer: A, B, D

Explanation

Options A, B, and D are correct because single row subqueries can indeed appear multiple times in a SQL statement, can be used in the WHERE clause to filter records, and can also be utilized in the HAVING clause for aggregate functions. Options C and E are incorrect as single row subqueries can be placed on either side of a comparison operator, and option F is inaccurate because a subquery can return NULL without causing an error, as long as the SQL handles it appropriately.