MySQL选择特定的行值作为列名
这是我的基本MySQL选择特定的行值作为列名,mysql,sql,pivot,Mysql,Sql,Pivot,这是我的基本参与者表(显示为关联数组): 在另一个名为participants\u custom的表中,我可以添加属于participants行的多个自定义数据。像这样: [id] => 51 [participant_id] => 1 [name] => textfield_bh423vjhgv [data] => qwerty1 [id] => 52 [participant_id] => 1 [name] => textfield_IDRr2kz
参与者表(显示为关联数组):
在另一个名为participants\u custom
的表中,我可以添加属于participants
行的多个自定义数据。像这样:
[id] => 51
[participant_id] => 1
[name] => textfield_bh423vjhgv
[data] => qwerty1
[id] => 52
[participant_id] => 1
[name] => textfield_IDRr2kzjZR59Xjw
[data] => qwerty2
[id] => 53
[participant_id] => 1
[name] => textfield_6kj5bhjjg
[data] => qwerty3
我目前正在创建一个加入
,但它只将名称
、参与者id
和数据
添加到我的行中。我希望我的查询返回如下内容:
[id] => 1
[campaign_id] => 41
[firstname] => Jeff
[lastname] => Berube
[textfield_bh423vjhgv] => qwerty1
[textfield_IDRr2kzjZR59Xjw] => qwerty2
[textfield_6kj5bhjjg] => qwerty3
行值name
变为列,value
变为值我该怎么做?
我找到了,但没有成功。我正在寻找一种适合我的情况的方法。谢谢你的帮助
SELECT a.ID,
a.Campaign_ID,
a.FirstName,
a.LastName,
MAX(CASE WHEN b.data = 'qwerty1' THEN b.Name END) qwerty1,
MAX(CASE WHEN b.data = 'qwerty2' THEN b.Name END) qwerty2,
MAX(CASE WHEN b.data = 'qwerty3' THEN b.Name END) qwerty3
FROM Participants a
INNER JOIN Participants_Custom b
ON a.ID = b.Participant_ID
GROUP BY a.ID,
a.Campaign_ID,
a.FirstName,
a.LastName
更新1
由于data
的值未知,因此更倾向于使用动态sql
SET @sql = NULL;
SELECT
GROUP_CONCAT(DISTINCT
CONCAT(
'MAX(CASE WHEN b.data = ''',
data,
''' THEN b.Name ELSE NULL END) AS ',
CONCAT('`',data, '`')
)
) INTO @sql
FROM Participants_Custom;
SET @sql = CONCAT('SELECT a.ID,
a.Campaign_ID,
a.FirstName,
a.LastName,', @sql,
'FROM Participants a
INNER JOIN Participants_Custom b
ON a.ID = b.Participant_ID
GROUP BY a.ID,
a.Campaign_ID,
a.FirstName,
a.LastName');
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
但是b.数据可以是任何东西,不仅仅是qwerty1、query2或qwerty3。如何判断b.Name中的值是否必须成为列,并将值
作为其值?并且参与者自定义
中的行数是可变的,大部分时间在0到6之间。然后需要动态sql,请稍候:D
SET @sql = NULL;
SELECT
GROUP_CONCAT(DISTINCT
CONCAT(
'MAX(CASE WHEN b.data = ''',
data,
''' THEN b.Name ELSE NULL END) AS ',
CONCAT('`',data, '`')
)
) INTO @sql
FROM Participants_Custom;
SET @sql = CONCAT('SELECT a.ID,
a.Campaign_ID,
a.FirstName,
a.LastName,', @sql,
'FROM Participants a
INNER JOIN Participants_Custom b
ON a.ID = b.Participant_ID
GROUP BY a.ID,
a.Campaign_ID,
a.FirstName,
a.LastName');
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;