SQL查詢與外鍵字段的表引用其他外鍵字段

Question

我已經在我的數據庫表的結構如下：

[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「工人」有外國鍵字段（「組合」）。 「組合」表具有一個字段名稱和一個外鍵字段「助手」，該助手再次是具有兩個外鍵字段的表格。

我的問題是，現在，什麼是最簡單的SQL查詢來獲取下表：

[table workers] 
ID [PK] | worker | combined-Name| department | location 
--------+--------+--------------+------------+----------- 
1  | John | name2  | Development| Paris 
--------------------------------+------------+----------- 
2  | Adam | name1  | Production | Berlin 

我試了一下已有的左JOINS但沒有管理它讓所有的「clearnames」來表中「工」

Answer 1

該查詢將工作：

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 

我用AS關鍵字的名稱設置爲您首選的輸出。

這在本地使用提供的結構和數據進行了測試。

它基本上是4個簡單的左連接，然後不是選擇ID的，而是選擇外表的名稱列。

上c.name別名被引用，因爲我們需要躲避特殊字符-

Answer 2

使用下面的查詢：

select [workers].worker,[combined].name as combined-name,[departments].name as department,[location].name as location from [workers] 
left join [combined] on [workers].combined = [combined].combined 
left join [helper] on [helper].ID = [combined].helper 
left join [departments] on [departments].ID = [helper].department 
left join [location] on [location].ID = [helper].location 

Answer 3

如果你是新來的MySQL，那麼你可以使用MySQL客戶端工具SQLyog其中有使用圖形界面生成查詢的查詢生成器