关于sequence的问题.currval和nextval

显示全部楼层 · 2005-10-30 17:05:33

you create a sequence with the following statement:
create sequence my_seq
start with 394
increment by 12
nominvalue
nomaxvalue
nocache
nocycle
Three user have alredy issued SQL statement to obtain NEXTVAL,and four more have issued SQL statements to obtain CURRVAL.if you issue a SQL statement to obtain the NEXTVAL ,what will oracle return?
A.406. B.418,C.430,D.442
书上给的答案是B.418
我算得是C.430
为什么?

千问 · 2005-10-30 17:05:33

在SEQUENCE有效的情况下，共计选择了4次NEXTVAL 所以应该是394＋48＝442，大家说对妈？

千问 · 2005-10-30 17:05:33

好像应该是430
因为第一次取nextval 返回的应该是394，然后再取三次nextval应当是返回430
其中取currval似乎不会影响其值

千问 · 2005-10-30 17:05:33

should be 418,
1st time: 394
2nd time: 394 + 12
3rd time 394+12+12 = 418
Note : Only 3 user refer to nextval

千问 · 2005-10-30 17:05:33

the answer is 430.
SQL> create sequence my_seq
2start with 394
3increment by 12
4nominvalue
5nomaxvalue
6nocache
7nocycle ;
SQL> select my_seq.nextval from dual;
NEXTVAL
----------
394
SQL> select my_seq.nextval from dual;
NEXTVAL
----------
406
SQL> select my_seq.nextval from dual;
NEXTVAL
----------
418
SQL> select MY_SEQ.CURRVAL from dual;
CURRVAL
----------
418
SQL> select my_seq.nextval from dual;
NEXTVAL
----------
430
勤动手，多实践！

千问 · 2005-10-30 17:05:33

那就是答案错了我对那本原版书的好印像完没了

千问 · 2005-10-30 17:05:33

序列没有初始化是不能用的.呵呵

千问 · 2005-10-30 17:05:33

原版书都出错,真伤心

千问 · 2005-10-30 17:05:33

应该是430=394+3*12

千问 · 2005-10-30 17:05:33

394+12*4=442