我在重置Oracle序列时遇到问题,因为MIN VALUE = 1并且使用的下一个号码是1。
我已经按照这个问题的答案: How do I reset a sequence in Oracle?
create or replace procedure reset_seq( p_seq_name in varchar2 ) is
l_val number;
begin
execute immediate
'select ' || p_seq_name || '.nextval from dual' INTO l_val;
execute immediate
'alter sequence ' || p_seq_name || ' increment by -' || l_val ||
' minvalue 0';
execute immediate
'select ' || p_seq_name || '.nextval from dual' INTO l_val;
execute immediate
'alter sequence ' || p_seq_name || ' increment by 1 minvalue 0';
end;
但是,问题是上面的代码重置了min值= 0的序列,下一个要使用的val是2.
重置完成后,是否可以将min_value = 1和nextval设置为1?
我试图设置它但是提到的错误大致如下:
当前值不能高于最小值。
谢谢!
答案 0 :(得分:1)
重置完成后,是否可以将最小值设置为1,并将下一个val设置为1?
你可以分两步完成:
逻辑是,你不应该将序列减少到零,因为你想要的 minvalue 是1
,所以, nextval不能小于minval 。
例如,
SQL> CREATE SEQUENCE s START WITH 20 MINVALUE 0 INCREMENT BY 1;
Sequence created.
SQL> SELECT s.nextval FROM dual;
NEXTVAL
----------
20
SQL> ALTER SEQUENCE s INCREMENT BY -19 MINVALUE 1;
Sequence altered.
SQL> SELECT s.nextval FROM dual;
NEXTVAL
----------
1
SQL> ALTER SEQUENCE s INCREMENT BY 1 MINVALUE 1;
Sequence altered.
SQL> SELECT s.nextval FROM dual;
NEXTVAL
----------
2
SQL> SELECT min_value, increment_by FROM user_sequences WHERE sequence_name='S';
MIN_VALUE INCREMENT_BY
---------- ------------
1 1
因此, min_value 和 increment_by 现在分别重置到1
。在将 increment_by 重新设置为1
之前, nextvalue 只能为1次。
所以,我没有看到你想要实现的任何实际用途。但是,它可以如上所示完成。
要在您的过程中实现上述逻辑,请执行以下操作:
<强>设置强>
SQL> DROP SEQUENCE S;
Sequence dropped.
SQL> CREATE SEQUENCE s START WITH 20 MINVALUE 0 INCREMENT BY 1;
Sequence created.
SQL> SELECT s.nextval FROM dual;
NEXTVAL
----------
20
将程序修改为:
SQL> CREATE OR REPLACE PROCEDURE reset_seq(
2 p_seq_name IN VARCHAR2 )
3 IS
4 l_val NUMBER;
5 BEGIN
6 EXECUTE IMMEDIATE 'select ' || p_seq_name || '.nextval from dual' INTO l_val;
7 l_val := l_val - 1;
8 dbms_output.put_line('l_val = '||l_val);
9 EXECUTE IMMEDIATE 'alter sequence ' ||
10 p_seq_name || ' increment by -' || l_val || ' minvalue 1';
11 EXECUTE IMMEDIATE 'select ' || p_seq_name || '.nextval from dual' INTO l_val;
12 dbms_output.put_line('1st Nextval is '||l_val);
13 EXECUTE IMMEDIATE 'alter sequence ' || p_seq_name ||
14 ' increment by 1 MINVALUE 1';
15 EXECUTE IMMEDIATE 'select ' || p_seq_name || '.nextval from dual' INTO l_val;
16 dbms_output.put_line('2nd Nextval is '||l_val);
17 END;
18 /
Procedure created.
SQL> SET serveroutput ON
SQL> EXEC reset_seq('S');
l_val = 20
1st Nextval is 1
2nd Nextval is 2
PL/SQL procedure successfully completed.
SQL>
SQL> SELECT min_value, increment_by FROM user_sequences where sequence_name='S';
MIN_VALUE INCREMENT_BY
---------- ------------
1 1
正如我所说,我没有看到任何实际用途。您的 nextval 实际上只能从2
使用。如果是1
,您需要再次执行 ALTER SEQUENCE ,将 increment_by 重置为1
。