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：
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