Oracle Database SQL — Question 214

Which two statements are true regarding the UNION and UNION ALL operators? (Choose two.)

Answer options

• A. Duplicates are eliminated automatically by the UNION ALL operator.
• B. The output is sorted by the UNION ALL operator.
• C. The names of columns selected in each SELECT statement must be identical.
• D. NULLs are not ignored during duplicate checking.
• E. The number of columns selected in each SELECT statement must be identical.

Correct answer: D, E

Explanation

The correct answers are D and E because NULLs are included in duplicate checking for both UNION and UNION ALL operators, and the number of columns must match in each SELECT statement to ensure proper execution. Options A and B are incorrect; UNION ALL does not eliminate duplicates, and it does not sort the output by default.