在oracle中添加自增字段id

自动增加字topicId

 CREATE TABLE t_topic (
 topicId       NUMBER(18,0)   NOT NULL  ,                       -- 主题ID
 topicTitle   VARCHAR2(100)  NOT NULL ,                         -- 主题名
 topicContent varchar2(2000) NOT NULL ,                       -- 主题内容
 ....
 PRIMARY KEY (topicId)
);

Create Sequence t_topic_Id_sequence                                    --主题序列
INCREMENT BY 1
START WITH 1
NOMAXVALUE
NOCYCLE;

CREATE OR REPLACE TRIGGER t_topic_Id_trigger //触发器
BEFORE INSERT
ON t_topic
FOR EACH ROW
DECLARE
newId NUMBER(18,0);
BEGIN
SELECT t_topic_Id_sequence.nextval INTO newId FROM dual;
:new.topicId := newId;
END;

来源:考试大- Oracle