Mysql递归查询 - 在错误的列中给出一些结果

Question

我有mysql表

    region_id | name | parent_id
    1 | Österreich   | 0
    3 | Deutschland  | 0
    4 | Bayern       | 3
    5 | Bad Griesbach| 4
    6 | Nordrhein-Westfalen| 3
    7  | Île-de-France | 7
    ....

我写了查询

        SELECT 

                h.hotel_id,
                h.hotel_name,
                t1.region_id,
                t1.name AS name1,
                t2.region_id,
                t2.name AS name2,
                t3.region_id,
                t3.name AS name3

            FROM
                hotel_service.hotel h
                LEFT JOIN region_service.region t1 ON t1.region_id = h.region_id
                LEFT JOIN region_service.region t2 ON t2.region_id = t1.parent_id
                LEFT JOIN region_service.region t3 ON t3.region_id = t2.parent_id

            WHERE
                hotel_id IN ('10640' , '10003', '10004', '10005', '10007')

结果是这样的

hotel_id hotel_name city_id name1   region_id   name2 region_id name3   
    10003   Dorfhotel    231    Sylt    30   Schleswig    3   Deutschland               
    10004   Iberotel    22  Boltenhagen 21  Mecklenburg   3   Deutschland               
    10005    Hotel  170    Barcelona   169  Katalonien   168    Spanien             
    10007   Schlosshotel 175 Rügen  21  Mecklenburg       3   Deutschland               
    10640   Hotel Berlin  36    Berlin  3   Deutschland                      

但结果顺序问题，例如hotel_id 10640 - 3 Deutschland显示在错误的列中，它应显示在最后一列，因为最后一列是country。

Answer 1

如果这是唯一有问题的案例，你可以试试这个;

SELECT 

                h.hotel_id,
                h.hotel_name,
                t1.region_id,
                t1.name AS name1,
case when t3.region_id is null then null else t2.region_id end,   
case when t3.region_id is null then null else t2.name end,      
case when t3.region_id is null then t2.region_id else t3.region_id end,   
case when t3.region_id is null then t2.name else t3.name end
            FROM
                hotel_service.hotel h
                LEFT JOIN region_service.region t1 ON t1.region_id = h.region_id
                LEFT JOIN region_service.region t2 ON t2.region_id = t1.parent_id
                LEFT JOIN region_service.region t3 ON t3.region_id = t2.parent_id

            WHERE
                hotel_id IN ('10640' , '10003', '10004', '10005', '10007')