OCP-1Z0-051-V9.02-43题

43. Evaluate the following CREATE SEQUENCE statement:

CREATE SEQUENCE seq1

START WITH 100

INCREMENT BY 10

MAXVALUE 200

CYCLE

NOCACHE;

The SEQ1 sequence has generated numbers up to the maximum limit of 200. You issue the following

SQL statement:

SELECT seq1.nextval FROM dual;

What is displayed by the SELECT statement?

A. 1

B. 10

C. 100

D. an error

Answer: A

 答案解析：

参考：http://blog.csdn.net/rlhua/article/details/12776779

实验验证：

1、首先创建这个序列

sh@TESTDB> CREATE SEQUENCE seq1

  2  START WITH 100

  3  INCREMENT BY 10

  4  MAXVALUE 200

  5  CYCLE

  6  NOCACHE;

 

Sequence created.

 2、查看值。

sh@TESTDB> select seq1.nextval from dual;

 

   NEXTVAL

----------

       100

 

sh@TESTDB> select seq1.currval from dual;

 

   CURRVAL

----------

       100

 3、因为该序列是循环的，到达最大值后从最小值MINVALUE开始循环，该序列因为省略MINVALUE省略，所以默认为NOMINVALUE最小值为 1，所有又从1开始。

sh@TESTDB> select seq1.nextval from dual;

 

   NEXTVAL

----------

       200

 

sh@TESTDB>

sh@TESTDB> select seq1.nextval from dual;

 

   NEXTVAL

----------

         1

 

 

 故答案选A