Oracle 中创建一触发器，要求完成：往表插入数据时，用触发器来完成序列的插入。

CREATE OR REPLACE TRIGGER triggerName BEFORE INSERT ON table t_user FOR EACH ROW
when (new.u_id is null)
begin
select user_seq.nextval into:new.id from dual;
end;
一般情况下会直接在程序里去调用序列，因为数据量太大的话，对表逐行扫描的话会影响性能

我感觉应该等他插入后，然后根据用户名来修改U_id
CREATE OR REPLACE TRIGGER insert_tuser_before
after INSERT ON t_user
FOR EACH ROW
BEGIN
update t_user set u_id=:new.user_seq.nextval where u_name=:new.u_name;
END ;

CREATE OR REPLACE TRIGGER trg_uid
BEFORE INSERT
ON t_user
REFERENCING NEW AS New OLD AS Old
FOR EACH ROW
BEGIN
Select user_seq.nextval
into :new.u_id
From DUAL;
END ;
/

buzhidao