Ti manca solo un gruppo per :)
SELECT PartNumber,
MAX(IF (Priority = 0, SupName, NULL)) AS Sup1,
MAX(IF (Priority = 1, SupName, NULL)) AS Sup2,
MAX(IF (Priority = 2, SupName, NULL)) AS Sup3
FROM SupXref
GROUP BY PartNumber
Modifica:
Dopo aver giocato per un po' penso di aver ottenuto la prima soluzione che stai cercando. Provalo :)
SELECT partnumber,
COALESCE(Sup1, COALESCE(Sup2, Sup3)) AS Supp1,
IF (Sup1 IS NULL, IF (Sup2 IS NULL, NULL, Sup3), COALESCE(Sup2, Sup3)) AS Supp2,
IF (Sup1 IS NULL, NULL, IF (Sup2 IS NULL, NULL, Sup3)) AS Supp3
FROM (
SELECT PartNumber,
MAX(IF (Priority = 0, SupName, NULL)) AS Sup1,
MAX(IF (Priority = 1, SupName, NULL)) AS Sup2,
MAX(IF (Priority = 2, SupName, NULL)) AS Sup3
FROM SupXref
GROUP BY PartNumber
) AS S
Per la tabella seguente:
+------------+----------+---------+
| PARTNUMBER | PRIORITY | SUPNAME |
+------------+----------+---------+
| a1 | 2 | Three |
| a2 | 1 | Two |
| a3 | 2 | Three |
| a3 | 1 | Two |
| a4 | 0 | One |
| a5 | 0 | One |
| a5 | 2 | Three |
| a6 | 0 | One |
| a6 | 1 | Two |
| a7 | 0 | One |
| a7 | 1 | Two |
| a7 | 2 | Three |
+------------+----------+---------+
I dati si trasformano in questo:
+------------+------+------+-------+
| PARTNUMBER | SUP1 | SUP2 | SUP3 |
+------------+------+------+-------+
| a1 | | | Three |
| a2 | | Two | |
| a3 | | Two | Three |
| a4 | One | | |
| a5 | One | | Three |
| a6 | One | Two | |
| a7 | One | Two | Three |
+------------+------+------+-------+
E infine in questo:
+------------+-------+-------+-------+
| PARTNUMBER | SUPP1 | SUPP2 | SUPP3 |
+------------+-------+-------+-------+
| a1 | Three | | |
| a2 | Two | | |
| a3 | Two | Three | |
| a4 | One | | |
| a5 | One | Three | |
| a6 | One | Two | |
| a7 | One | Two | Three |
+------------+-------+-------+-------+
