13. 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
then 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 REUSE clause when creating a sequence to restart the sequence once
it generates the maximum value defined for the sequence. 请问B与D哪个正确呢 我怎么觉得两个都正确啊~~~
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
then 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 REUSE clause when creating a sequence to restart the sequence once
it generates the maximum value defined for the sequence. 请问B与D哪个正确呢 我怎么觉得两个都正确啊~~~
B,D中应该有一个是正确的。
B对，CURRVAL只是查看，而D说是产生。(因为产生是由NEXTVAL来完成的）
1.Which statement is true about the GROUPING function? (Choose two.)
正确 A. It is used to find the groups forming the subtotal in a row.
B. It is used to identify the NULL value in the aggregate functions.
C. It is used to form the group sets involved in generating the totals and subtotals.
正确 D. It can only be used with ROLLUP and CUBE operators specified in the GROUP BY clause.
您选择的答案为：A,B不懂D中：grouping也可以用在没有rollup或cube的group by句子中啊~~~
D grouping set 使用，可以脱离rollup或cube使用