複雜的SQL查詢

Question

我有一個表，看起來像這樣：

meta_id post_id  meta_key meta_value 
271  4 _aciudad    New york 
270  4 _apais    USA 
267  10 _aservicio   Alojamiento 

... 
261  43 _apais    USA 
238  43 _aciudad    Chicago 
262  43 _aservicio   Alojamiento 
... 
261  43 _apais    USA 
238  43 _aciudad    Miami 
262  43 _aservicio   Alojamiento 

我需要做的，是顯示符合國家>市所有的寄存器。或ORDER BY全國所有_aciudad寄存器，是這樣的：

meta_id post_id meta_key meta_value  meta_key meta_value 
235  42  _aciudad  New York  _apais  USA 
236  56  _aciudad  Chicago  _apais  USA 
237  57  _aciudad  Miami  _apais  USA 
238  58  _aciudad  Sidney  _apais  Australia 
238  59  _aciudad  Melbourne _apais  Australia 

我不知道如何做到這一點，我想用INNER JOIN？雙重選擇？請幫幫我！！

Answer 1

SELECT t1.meta_id, 
      t1.post_id, 
      t1.meta_key, 
      t1.meta_value, 
      t2.meta_key, 
      t2.meta_value 
    FROM table t1, table t2 
    WHERE t1.post_id = t2.post_id 
    AND t1.meta_key = '_apais' 
    AND t2.meta_key = '_aciudad' 
    ORDER BY t1.meta_key 

Answer 2

SELECT mc.*, mp.meta_key, mp.meta_value 
FROM meta mc 
JOIN meta mp 
ON  mp.post_id = mc.post_id 
     AND mp.meta_key = '_apais' 
WHERE mc.meta_key = '_aciudad' 
ORDER BY 
     mp.meta_value, mc.meta_value 

Answer 3

我不知道這是否是你要找的東西，或者如果連接現場是正確的，因爲這不是你的問題很清楚，但這個怎麼查詢？

SELECT City.meta_id 
    , City.post_id 
    , City.meta_key 
    , City.meta_value 
    , Country.meta_key 
    , Country.meta_value 
    FROM yourTable City 
INNER JOIN yourTable Country ON City.post_id = Country.post_id 
WHERE City.meta_key = '_aciudad' AND Country.meta_key = '_apais' 
ORDER BY Country.meta_value, City.meta_value 

Answer 4

嘗試自我加入。爲了使它工作，你必須使用表的別名，所以你可以參考兩次。

事情是這樣的：

select 

    t1.meta_id, t1.post_id, 
    t1.meta_key, t1.meta_value, 
    t2.meta_key, t2.meta_value 

from TableName t1 
    inner join TableName t2 
    on t1.meta_id = t2.meta_id and t1.post_id = t2.post_id 
    and t1.meta_key = "_aciuidad" and t2.meta_key = "_apais"