ORACLE 创建表，利用序列和触发器实现主键自增长

//创建user 表
drop table t_user;
drop sequence s_user;
drop trigger tri_user;
create table t_user(
         id number(4) primary key,
         username varchar2(10) unique not null,
         password varchar2(50) not null,
         email varchar2(50),
         phone varchar2(50),
         question varchar2(50),
         answer varchar2(50),
         role number(4),
         create_time date,
        update_time date
);
create sequence s_user;
create trigger tri_user before
insert on t_user for each row when (new.id is null)
begin
 select s_user.nextval into:new.id from dual;
 end;
/
插入一行
insert into t_user (username,password,email,phone,question,answer,role,create_time,update_time) values ('wl2','123','3785@qq.com','1526113','我帅吗','帅',1,to_date('2018-08-06','YYYY-MM-DD'),sysdate)