Question

我有两张桌子：

Contacts:
+----+----+
|Name| #  |
+----+----+
|Joe | 123|
+----+----+
|Jane| 456|
+----+----+

Calls:
+----+----+
|To  |From|
+----+----+
|123 | 456|
+----+----+
|456 | 123|
+----+----+

我需要创建一个返回如下表的查询：

Log:
+------+------+------+------+
|To    |ToName|From  |FrName|
+------+------+------+------+
|123   | Joe  |  456 | Jane |
+------+------+------+------+
|456   | Jane |  123 | Joe  |
+------+------+------+------+

这在概念上似乎很简单，但我根本无法弄清楚如何将SQL拼凑在一起。我已经尝试了嵌套的SELECTS和嵌套的JOINS，但是无法让它正确运行（如果有的话）。提前谢谢。

Answer 1

您基本上需要将呼叫加入两个联系人副本：

SELECT ca.To,
       co1.Name AS ToName,
       ca.From,
       co2.Name AS FrName
FROM Contacts co1 INNER JOIN Calls ca
ON co1.[#] = ca.To INNER JOIN Contacts co2
ON co2.[#] = ca.From

Answer 2

我会这样做like this (SQL Fiddle)

SELECT c.to AS "To",
       t.name AS "ToName",
       c.from AS "From",
       f.name AS "FromName"
  FROM Calls c
  JOIN Contact AS t ON t.number = c.to
  JOIN Contact AS f ON f.number = c.from
 ORDER BY 1
;

如何基于输入上的两个单独字段和连接表上的一个字段加入表？

2 个答案: