将 Oracle 序列重置为 MIN VALUE = 1 和 STARTING 编号从 1

Question

我在将 Oracle 序列重置为 MIN VALUE = 1 并且开始使用的下一个数字是 1 时遇到问题。

我已经看完了这个问题的答案： 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，问题是上面的代码正在重置最小值 = 0 的序列，下一个要使用的值是 2。

是否可以在重置完成后设置 min_value = 1，nextval 为 1？

我尝试设置它，但收到大致如下所示的错误：

The current value cannot be higher then Minimum Value.

谢谢！

Answer 1

Is it possible to set the min value = 1, and next val to be 1, after the reset is done?

您可以分两步完成：

increment_by 值比序列的当前值小一。
将 increment_by 重置为 1。

逻辑是，你不应该将序列递减回零，因为你想要的最小值是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 reset 到 1 分别。在您再次将 increment_by 重置为 1 之前，nextvalue 只能为 1 一次。

因此，我没有看到您想要实现的任何实际用途。然而，它可以像上面演示的那样完成。

要在您的程序中实现上述逻辑，请执行以下操作：

设置

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

将您的程序修改为：

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，我没有看到它有任何实际用途。您的 nextval 实际上只能从 2 开始使用。当它是 1 时，您需要再次执行 ALTER SEQUENCE 以将 increment_by 重置回 1.

将 Oracle 序列重置为 MIN VALUE = 1 和 STARTING 编号从 1

Reset Oracle Sequence to have MIN VALUE = 1 and STARTING number from 1

oracle

sequence

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