动态数据透视表表mysql [英] Dynamic Pivot table columns mysql

问题描述

我有下表

人口统计类别

demographic_id  demographic_name
1               color
2               age_group

project_tests

test_id  group_id  project_id
1        1         1
2        1         1

test_demographic_requirements

test_id  project_id  demgraphic_id  demographic_value
1        1           1              blue
1        1           2              young
2        1           1              green
2        1           2              middle

我需要一个查询，该查询将给我以下结果:

And I need a query which would give me following result :

test_id  group_id  color  age_group 
1        1         blue   young
2        1         green  middle

我想我们需要使用数据透视表的概念来获取结果，但是我做不到.而且我的受众特征类别是否可以趋于相同，所以它们可能会发生变化，所以我需要动态的内容，那么什么是最好的方法?

I guess we need to use concept of pivot table to get the result, but I am unable to. And I demographic categories can we might be same they tend to change so I need something dynamic so what would be the best way to do it ?

我已经尝试根据以前的类似问题进行以下操作，但它似乎对我不起作用，这是我尝试过的操作:

I have tried doing the following based of previous similar questions but it doesn't seems to work for me, here is what I have tried:

SET @sql = NULL;
    SELECT
      GROUP_CONCAT(DISTINCT
        CONCAT(
          'max(case when dc.demographic_name = ''',
          demographic_name,
          ''' then trd.demographic_value end) AS ',
          replace(demographic_name, ' ', '')
        )
      ) INTO @sql
    from demographic_categories;

    SET @sql = CONCAT('SELECT pt.test_id, pt.group_id,
    ', @sql,'
    from test_requirement_demographic trd
    LEFT JOIN demographic_categories dc ON trd.demographic_id = dc.demographic_id
    LEFT JOIN project_tests pt ON pt.test_id = trd.test_id and project_id =1
    group by pt.test_id;');

    PREPARE stmt FROM @sql;
    EXECUTE stmt;

    DEALLOCATE PREPARE stmt;

推荐答案

您的动态SQL可以很好地运行，除了一件事.在您的第二个左连接处，它的列project_id含糊不清，只需将其替换为pt.project_id或trd.project_id，它将得到所需的结果.

Your dynamic SQL is just fine except for one thing. It has an ambiguous column project_id on your second left join, Just replace it with pt.project_id or trd.project_id and it will give desired result.

SET @sql = NULL;
    SELECT
      GROUP_CONCAT(DISTINCT
        CONCAT(
          'max(case when dc.demographic_name = ''',
          demographic_name,
          ''' then trd.demographic_value end) AS ',
          replace(demographic_name, ' ', '')
        )
      ) INTO @sql
    from demographic_categories;

SET @sql = CONCAT('SELECT pt.test_id, pt.group_id,
', @sql,'
from test_demographic_requirements trd
LEFT JOIN demographic_categories dc ON trd.demographic_id = dc.demographic_id
LEFT JOIN project_tests pt ON pt.test_id = trd.test_id and pt.project_id =1
group by pt.test_id;');

PREPARE stmt FROM @sql;
EXECUTE stmt;

DEALLOCATE PREPARE stmt;

我跑了一个月.这是链接: dynamic_pivot_test

I ran it on a rextester. Here is the link : dynamic_pivot_test

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