MySQL的 - 插入从一个表切换到另一个

Question

我有一个简单的表：

id  date  color 
---------------------- 
1 2012-01-01 black 
2 2012-01-02 red 
3 2012-01-03 red 
4 2012-01-04 red 
5 2012-01-05 green 

现在我需要插入从这个表中的颜色改变成新的：

date  before now 
---------------------------- 
2012-01-02 black red 
2012-01-04 red  green  

能

人告诉我怎么样，拜托？

Answer 1

比较第二行到上一行：

SELECT cur.date, prev.color "before", cur.color now 
FROM tbl cur 
LEFT JOIN tbl prev ON cur.id = prev.id + 1 
WHERE cur.id > 1 -- start detecting changes from second row 
    AND prev.color <> cur.color 

现场测试：http://sqlfiddle.com/#!2/0c146/1

编辑

在非连续数据甚至工作。查询可以，如果有CTE功能更succint在MySQL

create table tbl 
(
    id int, 
    date date, 
    color text 
); 


insert into tbl(id,date,color) 
select 1,'2012-1-1','black' union 
select 2,'2012-1-3','red' union 
select 3,'2012-1-7','red' union 
select 4,'2012-1-15','red' union 
select 5,'2012-1-21','green' ; 


set @rx = 0; 
set @ry = 0; 


select cur.date, prev.color as "before", cur.color as "now" 

from (select *, @ry := @ry + 1 as series from tbl order by date) as cur 
left join (select *, @rx := @rx + 1 as series from tbl order by date) as prev 
on cur.series = prev.series + 1 

where cur.series > 1 
and prev.color <> cur.color 

现场测试：http://sqlfiddle.com/#!2/b9443/2

Answer 2

首先，重命名color柱 - >before，然后添加now柱（default null如果可能的话），然后根据需要更新now柱。

Answer 3

如果我理解你的话，存储过程就是你需要的。

Stored Procedures