在oracle中使用sequence.nextval创建表

本文介绍了在oracle中使用sequence.nextval创建表的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我使用以下查询创建了一个序列，

i created a sequence using the following query,

create sequence qname_id_seq start with 1 increment by 1 nocache;

现在当我尝试创建一个使用上述序列的表时，会抛出以下错误，

Now when i try to create a table which uses the above sequence, it is throwing the following error,

Error report:
SQL Error: ORA-00907: missing right parenthesis
00907. 00000 -  "missing right parenthesis"

我使用以下查询创建一个包含sequence.nextval的表，

I used the following query to create a table with sequence.nextval,

CREATE TABLE qname
(
    qname_id integer NOT NULL default qname_id_seq.nextval PRIMARY KEY,
    qname    VARCHAR2(4000) NOT NULL -- CONSTRAINT qname_uk UNIQUE
);

Oracle 12c

我们现在终于有了许多其他数据库的 IDENTITY 列，以便在后台自动生成一个序列。此解决方案比基于触发器的解决方案快得多，，您不能这样做：

Oracle 11g and below

According to the documentation, you cannot do that:

在Oracle中有自动增量列的标准方法是使用触发器，例如

The standard way to have "auto increment" columns in Oracle is to use triggers, e.g.

CREATE OR REPLACE TRIGGER my_trigger
  BEFORE INSERT
  ON qname
  FOR EACH ROW
  -- Optionally restrict this trigger to fire only when really needed
  WHEN (new.qname_id is null)
DECLARE
  v_id qname.qname_id%TYPE;
BEGIN
  -- Select a new value from the sequence into a local variable. As David
  -- commented, this step is optional. You can directly select into :new.qname_id
  SELECT qname_id_seq.nextval INTO v_id FROM DUAL;

  -- :new references the record that you are about to insert into qname. Hence,
  -- you can overwrite the value of :new.qname_id (qname.qname_id) with the value
  -- obtained from your sequence, before inserting
  :new.qname_id := v_id;
END my_trigger;

详细了解

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