在Oracle中似乎没有AUTO_INCREMENT的概念,直到并包含版本11g.
如何在Oracle 11g中创建类似自动增量的列?
最佳答案
Oracle 11g中没有“自动增量”或“身份”列.但是,您可以使用序列和触发器轻松建模它:
表定义:
CREATE TABLE departments (
ID NUMBER(10) NOT NULL,
DESCRIPTION VARCHAR2(50) NOT NULL);
ALTER TABLE departments ADD (
CONSTRAINT dept_pk PRIMARY KEY (ID));
CREATE SEQUENCE dept_seq START WITH 1;
触发器定义:
CREATE OR REPLACE TRIGGER dept_bir
BEFORE INSERT ON departments
FOR EACH ROW
BEGIN
SELECT dept_seq.NEXTVAL
INTO :new.id
FROM dual;
END;
/
更新:
IDENTITY 列现在可用于Oracle 12c:
create table t1 (
c1 NUMBER GENERATED by default on null as IDENTITY,
c2 VARCHAR2(10)
);
或者指定启动和增量值,也防止任何插入身份列(GENERATED ALWAYS)(再次,Oracle 12c)
create table t1 (
c1 NUMBER GENERATED ALWAYS as IDENTITY(START with 1 INCREMENT by 1),
c2 VARCHAR2(10)
);
或者,Oracle 12也允许将序列作为默认值:
CREATE SEQUENCE dept_seq START WITH 1;
CREATE TABLE departments (
ID NUMBER(10) DEFAULT dept_seq.nextval NOT NULL,
DESCRIPTION VARCHAR2(50) NOT NULL);
ALTER TABLE departments ADD (
CONSTRAINT dept_pk PRIMARY KEY (ID));