oracle创建表相关

 --创建表
 create table person(
 id number primary key,
 name varchar2(40),
 birth date
 );
 --创建序列
 create sequence person_id_seq
 increment by 1
 start with 1
 nomaxvalue --不设置最大值
 nocycle  --一直累加，不循环
 cache 10;
 --创建触发器
 create or replace trigger person_id_tri before insert on person
 for each row
 declare
 v_newVal number(12) := 0;
 v_incval NUMBER(12) := 0;
 BEGIN
   IF INSERTING AND :new.id IS NULL THEN
     SELECT  person_id_SEQ.NEXTVAL INTO v_newVal FROM DUAL;
     -- If this is the first time this table have been inserted into (sequence == 1)
     IF v_newVal = 1 THEN
       --get the max indentity value from the table
       SELECT NVL(max(id),0) INTO v_newVal FROM person;
       v_newVal := v_newVal + 1;
       --set the sequence to that value
       LOOP
            EXIT WHEN v_incval>=v_newVal;
            SELECT person_id_seq.nextval INTO v_incval FROM dual;
       END LOOP;
     END IF;
     --used to emulate LAST_INSERT_ID()
     --mysql_utilities.identity := v_newVal;
    -- assign the value from the sequence to emulate the identity column
    :new.id := v_newVal;
   END IF;
 END;

 --简单触发器，上面触发器有问题,序列被跳过
 create or replace trigger person_id_tri before insert on person
 for each row when(new.id is null)
 BEGIN
 select person_id_seq.nextval into :new.id from dual;
 end;

 --插入实例
 insert into person(name, birth) values('ceshi',sysdate);
 --错误的时间格式
 insert into person(name,birth) values('hehe','2015-06-02 00:00:00');
 --正确的插入日期
 insert into person(name,birth) values('hehe',to_date('2005-01-01 13:14:20','yyyy-MM-dd HH24:mi:ss'));
 insert into person(name,birth) values('hehe',to_date('2005-01-01','yyyy-MM-dd'));

 --oracle 中日期的格式化
 select to_date('2005-01-01 13:14:20','yyyy-MM-dd HH24:mi:ss') from dual;

 --查询表
 select * from person ;

 --截断表
 truncate table person;