mysql - 内连接 - 单独的列

Question

我正在尝试将两个包含多个列的表链接在一起。例如，我有一个名为“wp_users”的表，我想将其用作主表，另一个表名为“CD2015_Occurrences”

我想将“wp_users”[EMAIL] 链接到 CD2015_Occurrences”[EMAIL]，这很简单但我想添加内部联接。

所以它看起来像这样

电子邮件 | Q1 | Q2 |第三季度 |第四季度 |

电子邮件1 | 2 | 4 | 5 | 6

电子邮件2 | 4 | 5 | 6 | 0

等等...

“CD2015_Occurrences”的表内容为电子邮件、季度、总计

我需要以某种方式通过电子邮件将它们链接到 wp_users，并且每个季度有 4 个单独的列。

我可能富裕，但这就是我正在尝试做的事情:

    Select a.user_email
FROM wp_users AS a
INNER JOIN a.email
ON CD2015_Occurrences.email as b (SELECT quarter AS Q1 FROM CD2015_Occurrences where email = a.email and quarter = 'q1')
INNER JOIN a.email
ON CD2015_Occurrences.email as b (SELECT quarter AS Q2 FROM CD2015_Occurrences where email = a.email and quarter = 'q2')
INNER JOIN a.email
ON CD2015_Occurrences.email as b (SELECT quarter AS Q3 FROM CD2015_Occurrences where email = a.email and quarter = 'q3')
INNER JOIN a.email
ON CD2015_Occurrences.email as b (SELECT quarter AS Q4 FROM CD2015_Occurrences where email = a.email and quarter = 'q4')

如果这可能的话，有什么想法吗？如何实现？ 非常感谢 最大

Answer 1

SELECT users.email,
   SUM(IF(occurences.quarter='q1',occurences.total,0)) Q1,
   SUM(IF(occurences.quarter='q2',occurences.total,0)) Q2,
   SUM(IF(occurences.quarter='q3',occurences.total,0)) Q3,
   SUM(IF(occurences.quarter='q4',occurences.total,0)) Q4
FROM wp_users users
LEFT JOIN CD2015_Occurrences occurrences
ON users.email = occurrences.email
GROUP BY users.email