I have a teacher table, and a phone table where the linking is by the person's ID. When I look up each professor's phone number, it looks like this:
(SELECT
T.ID_TEACHER,
P.PHONE,
P.NUMBER
FROM TEACHER T LEFT JOIN PHONES P
ON P.IDPERSON = T.ID_TEACHER)
| ID_TEACHER | Telephone | NUMBER |
|---|---|---|
| 1 | 1 | xxxxxxx |
| 1 | 2 | xxxxxxxx |
| 1 | 3 | xxxxxxx |
| 2 | 1 | xxxxxxx |
However, I want it to display like this:
| ID_TEACHER | Telephone | NUMBER | Telephone | NUMBER | Telephone | NUMBER |
|---|---|---|---|---|---|---|
| 1 | 1 | xxxxx | 2 | xxxxx | 3 | xxxxx |
| 2 | 1 | xxxxxxxxx |
what do I do? I'm using MYSQL. I didn't find a solution.
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You need to use conditional aggregation:
Try the following:
SELECT T.ID_TEACHER, MAX(CASE WHEN P.PHONE = 1 THEN P.PHONE ELSE NULL END) AS PHONE1, MAX(CASE WHEN P.PHONE = 1 THEN P.NUMBER ELSE NULL END) AS NUMBER1, MAX(CASE WHEN P.PHONE = 2 THEN P.PHONE ELSE NULL END) AS PHONE2, MAX(CASE WHEN P.PHONE = 2 THEN P.NUMBER ELSE NULL END) AS NUMBER2, MAX(CASE WHEN P.PHONE = 3 THEN P.PHONE ELSE NULL END) AS PHONE3, MAX(CASE WHEN P.PHONE = 3 THEN P.NUMBER ELSE NULL END) AS NUMBER3 FROM TEACHER T LEFT JOIN PHONES P ON P.IDPERSON = T.ID_TEACHER GROUP BY T.ID_TEACHER