Choose three缓存
Which three statements are true about sequences in a single instance Orade database?ide
A) A sequence's unallocated cached values are lost if the instance shuts down.three
B) Two or more tables cannot have keys generated from the same sequence.内存
C) A sequence number that was allocated can be rolled back if a transaction fails.it
D) A sequence can issue duplicate values.io
E) Sequences can always have gaps.table
F) A sequence can only be dropped by a DBA.class
Answer：：ADEtab
(解析：虚拟能够一会儿产生一组的数字缓存在内存中，可是实例关闭，没有用到的数字也将丢失;序列能够产生重复的值在定义的时候用 cycle 关键字，步长若是不是定义为 1，则产生的数字就不是连续的。)di