mysql - 使用自连接的最大值

Question

我有一个看起来像这样的表格...

mysql> select * from billing_order_history;
+----------+---------------+--------------+---------------------+
| order_id | modify_action | new_order_id | modified_by_user_id |
+----------+---------------+--------------+---------------------+
|       52 |             2 |           54 |                   1 | 
|       54 |             2 |           55 |                   1 | 
|       55 |             2 |           56 |                   1 | 
+----------+---------------+--------------+---------------------+
3 rows in set (0.00 sec)

旧订单 ID 已连接到新订单 ID。 52 >> 54 >> 55 >> 56

我需要返回最新的订单 ID，即原始订单 ID 52 的 56。

我编写了以下自连接，如果我在 where 子句中添加 b.order_id = 52，则该自连接不起作用。

select max(a.new_order_id) from billing_order_history as a inner join billing_order_history as b on a.order_id = b.new_order_id 

架构和示例记录:

 CREATE TABLE billing_order_history (
  order_id bigint(20) ,
  modify_action int(11) ,
  new_order_id bigint(20) ,
  modified_by_user_id bigint(20) 
) ;
insert into billing_order_history values (52, 2, 54, 1), (54, 2, 55, 1), (55,2,56,1);

Answer 1

你可以试试这个:

select max(latest)
from (
Select @latest:=case when @latest=order_id then new_order_id else @latest end
   as latest from billing_order_history, (select @latest:=55 ) as t
order by order_id) as t1;