Multiple choice technology databases

Which two statements about sequences are true? (Choose two.) A. You use a NEXTVAL pseudo column to look at the next possible value that would be generated from a sequence, without actually retrieving the value. B. You use a CURRVAL pseudo column to look at the current value just generated from a sequence, without affecting the further values to be generated from the sequence. C. You use a NEXTVAL pseudo column to obtain the next possible value from a sequence by actually retrieving the value from the sequence. D. You use a CURRVAL pseudo column to generate a value from a sequence that would be used for a specified database column. E. If a sequence starting from a value 100 and incremented by 1 is used by more than one application, then all of these applications could have a value of 105 assigned to their column whose value is being generated by the sequence. F. You use a REUSE clause when creating a sequence to restart the sequence once it generates the maximum value defined for the sequence.

  1. A

  2. B

  3. C

  4. D

  5. E

  6. F
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

The CURRVAL pseudo-column returns the value last generated by the sequence in the current session, while NEXTVAL increments and returns the next value.

AI explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) You use a NEXTVAL pseudo column to look at the next possible value that would be generated from a sequence, without actually retrieving the value. - This option is incorrect. The NEXTVAL pseudo column is used to retrieve the next value from a sequence, not just to look at it without retrieving it.

Option B) You use a CURRVAL pseudo column to look at the current value just generated from a sequence, without affecting the further values to be generated from the sequence. - This option is correct. The CURRVAL pseudo column is used to retrieve the current value generated from a sequence without affecting the sequence itself.

Option C) You use a NEXTVAL pseudo column to obtain the next possible value from a sequence by actually retrieving the value from the sequence. - This option is correct. The NEXTVAL pseudo column is used to retrieve the next value from a sequence by actually retrieving it from the sequence.

Option D) You use a CURRVAL pseudo column to generate a value from a sequence that would be used for a specified database column. - This option is incorrect. The CURRVAL pseudo column is used to retrieve the current value generated from a sequence, not to generate a new value.

Option E) If a sequence starting from a value 100 and incremented by 1 is used by more than one application, then all of these applications could have a value of 105 assigned to their column whose value is being generated by the sequence. - This option is incorrect. Each application will retrieve the next value from the sequence independently, so they will receive different values. In this case, each application will receive a different value after 100.

Option F) You use a REUSE clause when creating a sequence to restart the sequence once it generates the maximum value defined for the sequence. - This option is incorrect. The REUSE clause is not used to restart the sequence once it reaches the maximum value. It is used when dropping and recreating a sequence to reuse the existing values.

The correct answers are B) You use a CURRVAL pseudo column to look at the current value just generated from a sequence, without affecting the further values to be generated from the sequence. and C) You use a NEXTVAL pseudo column to obtain the next possible value from a sequence by actually retrieving the value from the sequence.

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