oracle 12c ocp 题库,最新oracle 12c OCP认证考试题库解析（2）

2.Which two statements are true about sequences created in a single instance database? (Choose two.)

A.CURRVAL is used to refer to the last sequence number that has been generated

B.DELETE would remove a sequence from the database

C.The numbers generated by a sequence can be used only for one table

D.When the MAXVALUE limit for a sequence is reached, you can increase the MAXVALUE limit by using the ALTER SEQUENCE statement

E.When a database instance shuts down abnormally, the sequence numbers that have been cached but not used would be available once again when the database instance is restarted。

解析:Oracle的序列

伪列currval获取当前序列的值，调用currval，必须先调用nextval的值。 A正确

使用DROP sequence_name删除序列 B错误

序列是共享的对象，可以用于多个表 C错误

当序列到达maxvalue，可以使用ALTER SEQUENCE xxx修改序列的最大值 D正确

当数据库被异常关闭后，序列的缓存的数字但没有使用重启数据库不能使用缓存的序列的值 E错误

Answer:AD