Question

编辑：可以找到此问题的扩展程序here 我想用SQLite加入四个不同的表，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。此外，每行的lon / lat值也不同。最佳输出将是：

+------+------+------+------+------+------+------+------+-----+-----+
|  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 |
+------+------+------+------+------+------+------+------+-----+-----+

同样，这是我的最终目标 - lat / lon值在表之间没有互连：
- a | b | c | .. | lat | lon |代替
- a | b | c | .. | table1.lat | table2.lat | ......
感谢您的帮助！
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

Answer 1

假设您的样本表包含如下数据

<强>表1：

a   b   lon lat
---------------
22  33  11  22

<强>表2：

c   d   lon lat
---------------
1   2   44  45

<强>表3

e       f       lon lat
-----------------------
NULL    NULL    100 101

<强>表4

g       h       lon lat
-----------------------
NULL    NULL    200 201

如果要合并记录，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

<强>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 |
+------+------+------+------+------+------+------+------+-----+-----+

<强> DEMO

SQLite：带有四个表的完全外连接

1 个答案: