它被称为Identity Columns，只能从oracle 12c获得

CREATE TABLE identity_test_tab
(
   id            NUMBER GENERATED ALWAYS AS IDENTITY,
   description   VARCHAR2 (30)
);

插入到标识列的示例如下

INSERT INTO identity_test_tab (description) VALUES ('Just DESCRIPTION');

已创建1行。

你不能像下面这样插入

INSERT INTO identity_test_tab (id, description) VALUES (NULL, 'ID=NULL and DESCRIPTION');

第1行错误:ORA-32795:不能插入生成的always 标识列

INSERT INTO identity_test_tab (id, description) VALUES (999, 'ID=999 and DESCRIPTION');

第1行错误:ORA-32795:不能插入生成的always 标识列

有用的链接

假设您指的是类似SQL Server标识列的列?

在Oracle中，您可以使用SEQUENCE来实现相同的功能。我看看能不能找到一个好的链接，然后贴在这里。

更新:看起来你自己找到了。这里是链接: http://www.techonthenet.com/oracle/sequences.php

在甲骨文12c以后，你可以这样做，

CREATE TABLE MAPS
(
  MAP_ID INTEGER GENERATED ALWAYS AS IDENTITY (START WITH 1 INCREMENT BY 1) NOT NULL,
  MAP_NAME VARCHAR(24) NOT NULL,
  UNIQUE (MAP_ID, MAP_NAME)
);

在Oracle (Pre 12c)中。

-- create table
CREATE TABLE MAPS
(
  MAP_ID INTEGER NOT NULL ,
  MAP_NAME VARCHAR(24) NOT NULL,
  UNIQUE (MAP_ID, MAP_NAME)
);

-- create sequence
CREATE SEQUENCE MAPS_SEQ;

-- create tigger using the sequence
CREATE OR REPLACE TRIGGER MAPS_TRG 
BEFORE INSERT ON MAPS 
FOR EACH ROW
WHEN (new.MAP_ID IS NULL)
BEGIN
  SELECT MAPS_SEQ.NEXTVAL
  INTO   :new.MAP_ID
  FROM   dual;
END;
/

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;

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;