Question

想知道是否有人可以提供帮助，我的SQL语句会让我感到悲伤。

我的声明使用MAX case（）作为数据透视表，工作正常 - 但我手动应用AS列名称 - 这可以动态完成吗？

这是我目前的陈述;

SELECT
u.prefix AS  'Title', 
u.forename AS  'Forename', 
u.surname AS  'Surname', 
u.email AS  'Email Address', 
u.update_time AS  'Register Date', 
eg.name AS 'Event Group Registered', 
e.name AS  'Session Registered', 
MAX(CASE WHEN uv.user_type_variables_id = 1 THEN uv.value ELSE NULL END) AS 'Question2',
MAX(CASE WHEN uv.user_type_variables_id = 2 THEN uv.value ELSE NULL END) AS 'Question2',
MAX(CASE WHEN uv.user_type_variables_id = 3 THEN uv.value ELSE NULL END) AS 'Question1',
MAX(CASE WHEN uv.user_type_variables_id = 4 THEN uv.value ELSE NULL END) AS 'Question2',
MAX(CASE WHEN uv.user_type_variables_id = 5 THEN uv.value ELSE NULL END) AS 'Question1',
MAX(CASE WHEN uv.user_type_variables_id = 6 THEN uv.value ELSE NULL END) AS 'Question2'

FROM tbl_event_attendees AS ea

LEFT JOIN tbl_user AS u ON ea.user_id = u.id
LEFT JOIN tbl_event AS e ON ea.event_id = e.id
LEFT JOIN tbl_event_groups AS eg on e.group_id = eg.id
LEFT JOIN tbl_user AS u2 ON ea.guest_of_user_id = u2.id
LEFT JOIN tbl_user_variables AS uv on u.id = uv.user_id

WHERE ea.event_id =6
GROUP BY ea.id

我的语句将几个表连接在一起，包括一个变量表，其中有几行适用于此表中的特定行。

所以我不希望列的名称是＆＃39;问题1＆＃39;，而是相邻的列＆＃39; name＆＃39;适用于uv.value，即。;

MAX(CASE WHEN uv.user_type_variables_id = 14 THEN uv.value ELSE NULL END) AS uv.name,

有谁能建议如何做到这一点？

Answer 1

不确定它是否适合您，但只是尝试一下;）

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'MAX(CASE WHEN uv.user_type_variables_id = ''',
      uv.user_type_variables_id,
      ''' THEN uv.value ELSE NULL END) AS `',
      uv.name, '`'
    )
  ) INTO @sql
FROM tbl_user_variables uv;
SET @sql = CONCAT('SELECT
        u.prefix AS  ''Title'', 
        u.forename AS  ''Forename'', 
        u.surname AS  ''Surname'', 
        u.email AS  ''Email Address'', 
        u.update_time AS  ''Register Date'', 
        eg.name AS ''Event Group Registered'', 
        e.name AS  ''Session Registered'', ',
        @sql, 
        ' FROM tbl_event_attendees AS ea
        LEFT JOIN tbl_user AS u ON ea.user_id = u.id
        LEFT JOIN tbl_event AS e ON ea.event_id = e.id
        LEFT JOIN tbl_event_groups AS eg on e.group_id = eg.id
        LEFT JOIN tbl_user AS u2 ON ea.guest_of_user_id = u2.id
        LEFT JOIN tbl_user_variables AS uv on u.id = uv.user_id
        WHERE ea.event_id =6
        GROUP BY ea.id');
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

使用MySQL数据透视表

1 个答案: