拥有这些表并需要加入它们以创建最终列表。
accounts
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| COMPANY_ID | COMPANY | ACCOUNT_OWNER |
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| 1 | bmw | 100 |
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| 2 | audi | 100 |
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| 3 | mercedes | 100 |
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| 4 | porsche | 200 |
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users
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| USER_ID | NAME |
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| 100 | bob |
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| 200 | sally |
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| 300 | mark |
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log_type
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| TYPE_ID | TYPE |
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| 1 | sales |
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| 2 | follow up |
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| 3 | marketing |
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logs (logs for each account)
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| COMPANY_ID | TYPE | USER | DATE | NOTE |
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| 1 | 2 | 200 | 2014-06-05 | 123 |
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| 1 | 2 | 100 | 2014-06-03 | ABC |
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| 1 | 2 | 100 | 2014-06-01 | 789 |
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| 1 | 3 | 100 | 2014-06-01 | XYZ |
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| 2 | 3 | 100 | 2014-01-01 | Hello |
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| 2 | 2 | 100 | 2014-01-01 | Hello |
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想要这些结果 - 显示一个用户的帐户表（在本例中为bob）。 - 显示附加到帐户的最后一个日志。 （如果没有，则显示无论如何/ NULL） - 仅拉取“跟进”类型的日志（（log_type.TYPE = 2） - 首先按最旧的附加日志对列表进行排序。 （logs.DATE asc）
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| COMPANY | TYPE | USER | DATE | NOTE |
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| audi | follow up | bob | 2014-01-01 | Hello |
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| bmw | follow up | bob | 2014-06-03 | ABC |
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| mercedes | NULL | bob | NULL | NULL |
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目前的代码看起来像这样......
select c.COMPANY, lt.TYPE, u.NAME, l.DATE, l.NOTE from accounts c
LEFT JOIN users u ON c.ACCOUNT_OWNER = u.USER_ID
LEFT JOIN logs l ON ( (c.ID_COMPANY = l.COMPANY) && l.TYPE = '2' && u.USER_ID = 100
LEFT JOIN log_type lt ON l.TYPE = lt.TYPE_ID
WHERE u.USER_ID = 100 && l.TYPE = '2'
GROUP BY c.COMPANY_ID
ORDER BY l.DATE asc