我的数据库中有以下表格结构：
[table workers]
ID [PK] | worker | combined [FK]
--------+--------+--------------+
1 | John | 2
--------------------------------+
2 | Adam | 1
[table combined]
ID [PK] | name | helper [FK]
--------+----------------------+
1 | name1 | 1
2 | name2 | 2
[table helper]
ID [PK] | department [FK] | location [FK]
--------+-------------+-------------------
1 | 2 | 3
2 | 1 | 1
[table departments]
ID [PK] | department
--------+-------------+
1 | Development |
2 | Production |
[table location]
ID [PK] | department
--------+--------------+
1 | Paris |
2 | London |
3 | Berlin |
表“workers”具有外键字段（“组合”）。表“combined”有一个字段名和一个外键字段“helper”，它也是一个带有两个外键字段的表。
我现在的问题是，获取下表的最简单的SQL查询是什么：
[table workers]
ID [PK] | worker | combined-Name| department | location
--------+--------+--------------+------------+-----------
1 | John | name2 | Development| Paris
--------------------------------+------------+-----------
2 | Adam | name1 | Production | Berlin
我已经尝试了一些LEFT-JOINS，但没有管理它以获得所有“清理”到表“工人”
答案 0 :(得分：1)
此查询可行：
SELECT w.ID, worker, c.name AS `combined-Name`, d.department, l.department as
location FROM workers w
LEFT JOIN combined c ON c.ID = w.combined
LEFT JOIN helper h ON h.ID = c.helper
LEFT JOIN departments d ON d.ID = h.department
LEFT JOIN location l ON l.ID = h.location
GROUP BY w.ID
我使用AS关键字将名称设置为首选输出。
使用提供的结构和数据在本地测试。
它基本上是4个简单的左连接，然后我选择了外来表的名称列，而不是选择ID。
引用了c.name上的别名，因为我们需要转义特殊字符-
答案 1 :(得分：-1)
使用以下查询：
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<tbody><tr>
<td>
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<tbody><tr>
<td height="40">
</td>
</tr>
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<tr>
<td align="center" valign="middle" style="line-height:0px;">
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</td>
</tr>
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</tbody></table>
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<tbody><tr>
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</td></tr>
</tbody></table>
</td>
</tr>
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</tbody></table>
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</td>
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</tbody></table>
</td>
</tr>
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<tr>
<td height="100" class="header-td">
</td>
</tr>
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<tr>
<td>
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<table class="zay600" width="600" border="0" align="center" cellpadding="0" cellspacing="0">
<tbody><tr>
<td align="center">
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<td align="center" style="line-height:0px;">
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</td>
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<tr>
<td height="100" class="header-td">
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</td>
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