将多个字段连接到另一个表中的一个字段

Question

我有两张桌子：

tblItinerary

ID | Place1 | Time1 | Place2 | Time2 | Place3 | Time3 |
1  | 1      |   10  |   2    |   23  |    1   |   21  |
2  | 2      |   5   |   3    |   4   |    1   |   12  |

tblPlaces

ID | PlaceName |
1  | Austria   |
2  | Germany   |
3  | India     |

我想要WHERE tblItinerary = 1来查看结果集：

Place1  | Place2  | Place3  |
Austria | Germany | Austria |

现在我的方向就像是

SELECT tblPlaces.PlaceName
 FROM tblPlaces
 JOIN tblPlaces.PlaceName
 ON tblItinerary.Place1 = tblPlaces.PlaceName
 JOIN tblPlaces.PlaceName
 ON tblItinerary.Place2 = tblPlaces.PlaceName
 JOIN tblPlaces.PlaceName
 ON tblItinerary.Place3 = tblPlaces.PlaceName
 WHERE tblItinerary.ID = 1;

Answer 1

这个想法是正确的，但是有一些错误：要多次连接一个表，你应该为每个表使用唯一的别名。此外，您实际上并未在任何地方加入tblItinerary，并且您的加入语法不正确（您尝试加入tblPlaces.PlaceName而不是tblPlaces）。请尝试以下方法：

select p1.PlaceName as Place1
     , p2.PlaceName as Place2
     , p3.PlaceName as Place3
from tblItinerary i
join tblPlaces p1 on i.Place1 = p1.ID
join tblPlaces p2 on i.Place2 = p2.ID
join tblPlaces p3 on i.Place3 = p3.ID
where i.ID = 1;