完全外部加入在4個表上的sqlite

Question

我需要基於一個公共主鍵聯接4個表。如果sqlite實現完全外連接，它可能看起來像這樣（不考慮優化）。

SELECT S.pair, C.ball, P.bluejeans, B.checkered 
FROM Socks S 
FULL OUTER JOIN Caps C 
FULL OUTER JOIN Pants P 
FULL OUTER JOIN Boxers B 
WHERE S.color = C.color AND S.color = P.color AND S.color = B.color; 

我看着漫長而艱難的，我發現最好的是這2臺sqlite的FULL JOIN左聯接和工會承滴盤實現：

SELECT employee.*, department.* 
FROM employee LEFT JOIN department 
ON employee.DepartmentID = department.DepartmentID 
UNION ALL SELECT employee.*, department.* 
FROM department LEFT JOIN employee 
ON employee.DepartmentID = department.DepartmentID 
WHERE employee.DepartmentID IS NULL; 

我試圖修改此工作對於超過2個表格，但我是新來的SQL，我沒有太多。是否有可能在合理的時間內得到這個結果？

我想我有3個表正確執行（這可能是不正確），但我似乎仍不能得到它爲4.這是我有3：

SELECT S.pair, C.ball, P.bluejeans 
FROM Socks S LEFT JOIN Caps C LEFT JOIN Pants P 
ON C.color = S.color AND P.color = S.color 
UNION ALL 
SELECT S.pair, C.ball, P.bluejeans 
FROM Socks S LEFT JOIN Caps C LEFT JOIN Pants P 
ON S.color = C.color AND S.color = P.color 
WHERE S.color IS NULL; 

任何幫助非常感謝

Answer 1

的全外的一般建設兩個表A和B SQLite中的確是之間的連接：

SELECT ... FROM A LEFT JOIN B ON ... 
UNION ALL 
SELECT ... FROM B LEFT JOIN A ON ... WHERE A.key IS NULL 

現在create a viewSocksCaps爲全外連接Socks和Caps之間：

CREATE VIEW SocksCaps AS 
SELECT ... FROM Socks LEFT JOIN Caps ON ... 
UNION ALL 
SELECT ... FROM Caps LEFT JOIN Socks ON ... WHERE Socks.color IS NULL 

執行相同的Pants和Boxers。

然後把這些意見就像表，做一個完整的外部以相同結構加入：

SELECT ... FROM SocksCaps LEFT JOIN PantsBoxers ON ... 
UNION ALL 
SELECT ... FROM PantsBoxers LEFT JOIN SocksCaps ON ... WHERE SocksCaps.color IS NULL