Question

I have a SQL situation for which I don’t have a solution.

Combinations of locations are defined in table PressureBox in which DD and CR are both Foreign Keys to the Location table.

Table Location

+--------+--------+
| ID     | Name   |
+--------+--------+
| KPN1   | AA     |
| MIN2   | BB     |
| KGM10  | CC     |
| KST100 | DD     |
+--------+--------+

Table PressureBox

+--------+--------+
| DD     | CR     |
+--------+--------+
| KPN1   | KGM10  |
| MIN2   | KST100 |
+--------+--------+

I’m trying to get the following resultset:

+-------+-------+
| Loc1  | Loc2  |
+-------+-------+
| AA    | BB    |
| CC    | DD    |
+-------+-------+

(from table Location, Name aliased as Loc1/Loc2)

So for example, KPN1 + KGM10 must result in “AA | CC”.

How can this be accomplished in SQL? Any ideas, solutions or hints are welcome. Thanks.

Answer 1

SELECT 
    Loc1.Name AS Loc1,
    Loc2.Name AS Loc2
FROM
    PressureBox PB
    JOIN Location Loc1 ON Loc1.ID = PB.DD
    JOIN Location Loc2 ON Loc2.ID = PB.CR