Orcal数据库实现主键ID自增

转：http://www.jb51.net/article/53004.htm
CREATE TABLE ADVICE
(
ID INT NOT NULL,
ACTIVE INT DEFAULT 1 NOT NULL,
TYPE INT NOT NULL, 
MSG VARCHAR2(512) NOT NULL,
ADVICE VARCHAR2(4000) NOT NULL,
PRIMARY KEY(ID),
CONSTRAINT ADVICE_UNI UNIQUE(TYPE,MSG)
)TABLESPACE MYDB;

--创建自增ID，名称为：表名_字段名_SEQ
CREATE SEQUENCE ADVICE_ID_SEQ MINVALUE 1 NOMAXVALUE INCREMENT BY 1 START WITH 1 NOCACHE;


-- 为Insert操作创建触发器，无需在SQL语句里写NEXTVAL，名称为表名_INS_TRG
CREATE OR REPLACE TRIGGER ADVICE_INS_TRG BEFORE INSERT ON ADVICE FOR EACH ROW WHEN(NEW.ID IS NULL)
BEGIN
SELECT ADVICE_ID_SEQ.NEXTVAL INTO :NEW.ID FROM DUAL;
END;