Oracle Database SQL — Question 256

Which two are true about queries using set operators (UNION, UNION ALL, INTERSECT and MINUS)? (Choose two.)

Answer options

• A. The name of each column in the first SELECT list must match the name of the corresponding column in each subsequent SELECT list.
• B. None of the set operators can be used when selecting CLOB columns.
• C. There must be an equal number of columns in each SELECT list.
• D. Each SELECT statement in the query can have an ORDER BY clause.
• E. The FOR UPDATE clause cannot be specified.

Correct answer: C, E

Explanation

The correct answer is C and E because each SELECT list must indeed have an equal number of columns for the set operators to function correctly. Additionally, the FOR UPDATE clause cannot be used with these operators. Options A, B, and D are incorrect as they either misrepresent requirements or restrictions that do not apply to all set operator scenarios.