Oracle Database SQL — Question 32

Which three statements are true about sequences in a single instance Oracle database? (Choose three.)

Answer options

• A. A sequence’s unallocated cached values are lost if the instance shuts down.
• B. A sequence number that was allocated can be rolled back if a transaction fails.
• C. A sequence can only be dropped by a DBA.
• D. A sequence can issue duplicate values.
• E. Sequences can always have gaps.
• F. Two or more tables cannot have keys generated from the same sequence.

Correct answer: A, D, E

Explanation

Option A is correct because unallocated cached values are indeed lost when an instance shuts down. Option D is correct as sequences can generate duplicate values under certain conditions. Option E is also accurate since sequences can have gaps due to various reasons like caching. Options B, C, and F are incorrect because allocated sequence numbers are not rolled back, sequences can be dropped by any user with the necessary privileges, and multiple tables can share the same sequence for key generation.