将多行合并到一个MySQL中 [英] Combine multiple rows into one MySQL

问题描述

我需要一些帮助.我用谷歌搜索了解决方案，但没有找到解决方法.

I need some help. I googled for solution, but I didn't found one.

我有三个表:

langs
(int) id | (varchar) language
    1    |       English
    2    |        Latin
    3    |      Esperanto
   ...   |         ...

keys
(int) id | (varchar) keys
    1    |       dog
    2    |       cat
   ...   |       ...

value
(int) id | (int) key_id | (int) lang_id | (varchar) value
    1    |       1      |        1      |        Dog
    2    |       1      |        2      |       Canis
    3    |       2      |        1      |        Cat
    4    |       2      |        2      |       Felis
    5    |       2      |        3      |        Kato
   ...   |      ...     |       ...     |        ...

我想得到结果:

key_id |  keys  |  English  |  Latin  |  Esperanto  
   1   |  dog   |    Dog    |  Canis  |    NULL
   2   |  cat   |    Cat    |  Felis  |    Kato
  ...  |  ...   |    ...    |   ...   |    ...

合并等于key_id的行.我知道我可以尝试使用多个JOIN来做到这一点，但这很慢，而且我必须知道不同langs的确切数目.

merging rows with equal key_id. I know I can try to make it with multiple JOINs, but it's slow and I must know the exact number of different langs.

先谢谢了. :)

推荐答案

SELECT CONCAT(
  ' SELECT `value`.`key_id`,'
,        '`keys`.`keys`,'
,         GROUP_CONCAT(
           'GROUP_CONCAT(IF(`value`.`lang_id`=',id,',`value`.`value`,NULL))'
          ,   ' AS `', REPLACE(language, '`', '``'), '`'
          )
, ' FROM `keys` JOIN `value` ON `value`.`key_id` = `keys`.`id`'
, ' GROUP BY `value`.`key_id`'
)
INTO @sql
FROM `langs`;

PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

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