将多个字段连接到另一个表中的一个

Question

I have two tables:

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     |

I want do a WHERE tblItinerary = 1 to see the result set as:

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

Right now the direction I have is something like

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

The idea is correct, but there are some mistakes: to join one table multiple times, you should use unique aliases for each table. Also, you have not actually joined tblItinerary anywhere and your join syntax is incorrect (your attempt to join tblPlaces.PlaceName instead of tblPlaces ). Try the following:

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;