拉鏈表

/*拉鏈表: 也就是一個 記錄歷史 表,用於記錄事物從 最開始的狀態 到 當前狀態 所有變化的信息 */

--歷史表
drop table old_tb_his;
drop table new_tb;


--od 我們希望的拉鏈表記錄數據的所有狀態，初始化為昨日全量數據
create table old_tb_his(
id  number(10,0),
status  varchar2(20),
start_date varchar2(20),
end_date varchar2(20)
);
insert into old_tb_his values(1,'1', '200712' , '299901');
insert into old_tb_his values(2,'2', '200712' , '299901');
insert into old_tb_his values(3,'3', '200712' , '299901');
insert into old_tb_his values(4,'4', '200712' , '299901');
insert into old_tb_his values(5,'5', '200712' , '299901');
commit;
select * from old_tb_his;


--nd 今日全量數據
create table new_tb as select * from old_tb_his where 2 = 1 ;
insert into new_tb values(1,'2', '200801' , '299901');
insert into new_tb values(2,'2', '200801' , '299901');
insert into new_tb values(3,'4', '200801' , '299901');
insert into new_tb values(4,'4', '200801' , '299901');
insert into new_tb values(5,'6', '200801' , '299901');
commit;
select * from new_tb;


/*merge into old_tb_his
 using new_tb
 on (old_tb_his.id = new_tb.id and old_tb_his.status = new_tb.status )
when matched then  update set old_tb_his.end_date =  new_tb.start_date
when not matched then insert values(new_tb.id, new_tb.status, new_tb.start_date,new_tb.end_date);*/


/*
用不了  這個函數是匹配就更新   不匹配添加
   而拉鏈算法可以看作是 不匹配的更新 不匹配的也添加
*/
/*merge into old_tb_his
 using new_tb
 on (old_tb_his.id = new_tb.id and old_tb_his.status = new_tb.status )
when not matched then update set old_tb_his.end_date =  new_tb.start_date ;
when not matched then insert values(new_tb.id, new_tb.status, new_tb.start_date,new_tb.end_date);
*/
--如果函數不能完成拉鏈算法 只能通過存儲過程來完成
select * from old_tb_his;
select * from new_tb;


drop table old_tb_his_temp;
drop table new_tb_temp;
--創建臨時表old_tb_his_temp
create global temporary  table old_tb_his_temp
(
id  number(10,0),
status  varchar2(20),
start_date varchar2(20),
end_date varchar2(20)
)
on commit delete rows ;

--創建臨時表new_tb_temp
create global temporary  table new_tb_temp
(
id  number(10,0),
status  varchar2(20),
start_date varchar2(20),
end_date varchar2(20)
)
on commit delete rows ;


-- w_i = nd - od  (  將w_i表的內容全部插入到歷史表中，這些是新增記錄 )
--今日全量數據減去拉鏈表數據 等於新增數據 用w_i表示
--UNION(無重並集)、UNION ALL(有重並集)、INTERSECT(交集)、MINUS (差集)：只顯示在第一個集合中存在，在第二個集合中不存在的數據
insert into old_tb_his_temp
  select *
    from new_tb t
   where t.id not in (select id--今日全量數據，減去拉鏈表數據和今日全量數據的交集，等於今日新增數據
                        from (select t1.id, t1.status, t1.end_date
                                from old_tb_his t1
                              intersect
                              select t2.id, t2.status, t2.end_date
                                from new_tb t2));--查詢拉鏈表數據和今日全量數據的交集

-- w_u = od - nd ( 對歷史表進行w_u部份的更新操作，start_date保持不變，而end_date改為當天 )封鏈
insert into new_tb_temp
select *
  from old_tb_his t
 where t.id not in (select id--拉鏈表數據，減去拉鏈表數據和今日全量數據的交集，等於待更新數據
                      from (select t1.id, t1.status, t1.end_date
                              from old_tb_his t1
                            intersect
                            select t2.id, t2.status, t2.end_date
                              from new_tb t2));--查詢拉鏈表數據和今日全量數據的交集
--查詢兩個臨時表
select * from old_tb_his_temp;
select * from new_tb_temp;
commit;

--insert操作把w_i插入到拉鏈表
insert into old_tb_his
select * from old_tb_his_temp ;
--查詢是否成功插入
--select * from old_tb_his ;


--多表更新語句一: update 操作按u更新his
/*merge into old_tb_his
using  old_tb_his_temp on (old_tb_his.id = old_tb_his_temp.id and old_tb_his.status <> old_tb_his_temp.status )
 when matched then update set old_tb_his.end_date = old_tb_his_temp.start_date ;*/

--多表更新語句二: or: update 操作按u更新his
update old_tb_his
set old_tb_his.end_date = (select old_tb_his_temp.start_date from old_tb_his_temp  where old_tb_his_temp.id = old_tb_his.id)
where exists(
select 1 from old_tb_his_temp where old_tb_his.id = old_tb_his_temp.id
                                and old_tb_his.status <> old_tb_his_temp.status
);

commit;


select * from old_tb_his

用戶標志       狀態 開始時間 結束時間
1               1   200712  200801 --change
2               2   200712  299901
3               3   200712  200801 --change
4               4   200712  299901
5               5   200712  200801 --change
1               2   200801  299901
3               4   200801  299901
5               6   200801  299901