ORACLE中建立自增字段的方法

今天有人问起，写在这里，便于以后CP


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1. 建立 SEQUENCE

CREATE [ OR REPLACE ] SEQUENCE sequence_identity
START WITH [b]initial seed
[/b]INCREMENT BY [b]step
[/b]MAXVALUE upper bound [NOMAXVALUE]
NOCYCLE [empty]

2. 建立 TRIGGER

CREATE [ OR REPLACE ] TRIGGER trigger_identity
BEFORE INSERT ON table_name
FOR EACH ROW
BEGIN
SELECT sequence_identity.NEXTVAL INTO :new.column_name FROM DUAL;
END;