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我想用SQLite联接四个不同的表，它们只有两个共同的列。请看下面的例子
+--------+---+-----+-----+
| table1 | | | |
+--------+---+-----+-----+
| a | b | lon | lat |
+--------+---+-----+-----+
| 1 | 2 | 111 | 222 |
+--------+---+-----+-----+
+--------+---+-----+-----+
| table2 | | | |
+--------+---+-----+-----+
| c | d | lon | lat |
+--------+---+-----+-----+
| 3 | 4 | 333 | 444 |
+--------+---+-----+-----+
+--------+---+-----+-----+
| table3 | | | |
+--------+---+-----+-----+
| e | f | lon | lat |
+--------+---+-----+-----+
| 5 | 6 | 555 | 666 |
+--------+---+-----+-----+
+--------+---+-----+-----+
| table4 | | | |
+--------+---+-----+-----+
| g | h | lon | lat |
+--------+---+-----+-----+
| 7 | 8 | 777 | 888 |
+--------+---+-----+-----+
这些表未通过任何外键连接。同样，每行的lon / lat值也不同。最佳输出为：
+------+------+------+------+------+------+------+------+-----+-----+
| a | b | c | d | e | f | g | h | lon | lat |
+------+------+------+------+------+------+------+------+-----+-----+
| None | None | 3 | 4 | None | None | None | NOne | 333 | 444 |
| 1 | 2 | None | None | None | None | None | None | 111 | 222 |
| None | None | None | None | 5 | 6 | None | None | 555 | 666 |
| None | None | None | None | None | None | 7 | 8 | 777 | 888 |
+------+------+------+------+------+------+------+------+-----+-----+
再次，这是我的最终目标-表格之间的经/纬度值未互连：
一个| b | c | .. | lat | lon |代替
一个| b | c | .. | table1.lat | table2.lat | ...
感谢你的帮助！
我当前的代码
-- First two tables
CREATE VIEW ab AS
SELECT * FROM table1 LEFT JOIN table2 ON ???
UNION ALL
SELECT * FROM table2 LEFT JOIN table1 ON ?? WHERE ?? IS NULL
-- 3rd and 4th table
CREATE VIEW cd AS
SELECT * FROM table3 LEFT JOIN table4 ON ??
UNION ALL
SELECT * FROM table4 LEFT JOIN table3 ON ?? WHERE ?? IS NULL
-- -- JOIN
SELECT * FROM cd LEFT JOIN ab ON ??
UNION ALL
SELECT * FROM cd LEFT JOIN ab ON ?? WHERE ?? IS NULL
最佳答案
假设您的样本表具有如下数据
表格1：
a b lon lat
---------------
22 33 11 22
表2：
c d lon lat
---------------
1 2 44 45
表3
e f lon lat
-----------------------
NULL NULL 100 101
表4
g h lon lat
-----------------------
NULL NULL 200 201
并且要合并记录，可以使用
union all。select a,b,NULL as c, NULL as d,NULL as e, NULL as f, NULL as g, NULL as h, lon,lat
from table1
union all
select NULL, NULL,c,d,NULL as e, NULL as f, NULL as g, NULL as h, lon,lat
from table2
union all
select NULL, NULL,NULL,NULL,e,f, NULL as g, NULL as h, lon,lat
from table3
union all
select NULL, NULL,NULL,NULL,NULL,NULL,g,h, lon,lat
from table4
结果：
+------+------+------+------+------+------+------+------+-----+-----+
| a | b | c | d | e | f | g | h | lon | lat |
+------+------+------+------+------+------+------+------+-----+-----+
| 22 | 33 | NULL | NULL | NULL | NULL | NULL | NULL | 11 | 22 |
| NULL | NULL | 1 | 2 | NULL | NULL | NULL | NULL | 44 | 45 |
| NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | 100 | 101 |
| NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | 200 | 201 |
+------+------+------+------+------+------+------+------+-----+-----+
DEMO
关于sql - SQLite:具有四个表的完全外部联接，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/47666005/