复杂的SQL查询

Question

我有一个表，看起来像这样：

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，是显示符合国家>市所有的寄存器。或ORDER BY全国所有_aciudad寄存器，是这样的：

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 

我不知道如何做到这一点，我想用INNER JOIN？双重选择？请帮帮我！！

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

我不知道这是否是你要找的东西，或者如果连接现场是正确的，因为这不是你的问题很清楚，但这个怎么查询？

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

尝试自我加入。为了使它工作，你必须使用表的别名，所以你可以参考两次。

事情是这样的：

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"