在Oracle中似乎没有AUTO_INCREMENT的概念,直到并且包括版本11g。
如何在Oracle 11g中创建一个行为像自动递增的列?
在Oracle中似乎没有AUTO_INCREMENT的概念,直到并且包括版本11g。
如何在Oracle 11g中创建一个行为像自动递增的列?
当前回答
也许可以试试这个简单的脚本:
http://www.hlavaj.sk/ai.php
结果是:
CREATE SEQUENCE TABLE_PK_SEQ;
CREATE OR REPLACE TRIGGER TR_SEQ_TABLE BEFORE INSERT ON TABLE FOR EACH ROW
BEGIN
SELECT TABLE_PK_SEQ.NEXTVAL
INTO :new.PK
FROM dual;
END;
其他回答
Oracle数据库12c引入了Identity,一个自动增量(系统生成)列。 在以前的数据库版本中(直到11g),您通常通过创建Sequence和Trigger来实现Identity。 从12c开始,您可以创建自己的Table并定义必须作为Identity生成的列。
FUNCTION GETUNIQUEID_2 RETURN VARCHAR2
AS
v_curr_id NUMBER;
v_inc NUMBER;
v_next_val NUMBER;
pragma autonomous_transaction;
begin
CREATE SEQUENCE sequnce
START WITH YYMMDD0000000001
INCREMENT BY 1
NOCACHE
select sequence.nextval into v_curr_id from dual;
if(substr(v_curr_id,0,6)= to_char(sysdate,'yymmdd')) then
v_next_val := to_number(to_char(SYSDATE+1, 'yymmdd') || '0000000000');
v_inc := v_next_val - v_curr_id;
execute immediate ' alter sequence sequence increment by ' || v_inc ;
select sequence.nextval into v_curr_id from dual;
execute immediate ' alter sequence sequence increment by 1';
else
dbms_output.put_line('exception : file not found');
end if;
RETURN 'ID'||v_curr_id;
END;
这是我如何在一个现有的表和列(名为id)上做到这一点:
UPDATE table SET id=ROWNUM;
DECLARE
maxval NUMBER;
BEGIN
SELECT MAX(id) INTO maxval FROM table;
EXECUTE IMMEDIATE 'DROP SEQUENCE table_seq';
EXECUTE IMMEDIATE 'CREATE SEQUENCE table_seq START WITH '|| TO_CHAR(TO_NUMBER(maxval)+1) ||' INCREMENT BY 1 NOMAXVALUE';
END;
CREATE TRIGGER table_trigger
BEFORE INSERT ON table
FOR EACH ROW
BEGIN
:new.id := table_seq.NEXTVAL;
END;
在Oracle 11g中没有“auto_increment”或“identity”列这样的东西。然而,你可以很容易地用一个序列和一个触发器来建模:
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列现在可以在Oracle 12c上使用:
create table t1 (
c1 NUMBER GENERATED by default on null as IDENTITY,
c2 VARCHAR2(10)
);
或者指定起始值和增量值,同时防止任何插入标识列(GENERATED ALWAYS)(同样,仅适用于Oracle 12c+)
create table t1 (
c1 NUMBER GENERATED ALWAYS as IDENTITY(START with 1 INCREMENT by 1),
c2 VARCHAR2(10)
);
另外,Oracle 12也允许使用一个序列作为默认值:
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));
也许可以试试这个简单的脚本:
http://www.hlavaj.sk/ai.php
结果是:
CREATE SEQUENCE TABLE_PK_SEQ;
CREATE OR REPLACE TRIGGER TR_SEQ_TABLE BEFORE INSERT ON TABLE FOR EACH ROW
BEGIN
SELECT TABLE_PK_SEQ.NEXTVAL
INTO :new.PK
FROM dual;
END;