MYSQL - 查詢獲取不同的 sender_id、receiver id 和 richiesta_id

Question

我有這個表“消息”結果：

我試過：

SELECT idutente, richiesta_id
FROM (
  SELECT sender_id, richiesta_id
  FROM messages
  UNION
  SELECT receiver_id, richiesta_id
  FROM messages
) AS DistinctCodes (idutente)
WHERE idutente IS NOT NULL;

但不工作或不正確。 我怎樣才能從表中得到你看到的表：

|    richiesta_id     |                users                |
|---------------------|-------------------------------------|
| 55                  | 2, 3, 4                             |
| other richiesta_id  | other users list separated by comma |

Answer 1

我認為您需要結合使用“GROUP BY”和“GROUP_CONCAT”來歸檔它。

SELECT DistinctCodes.richiesta_id, GROUP_CONCAT(DISTINCT DistinctCodes.uid ORDER BY DistinctCodes.uid ASC)
FROM (
  SELECT sender_id AS uid, richiesta_id
  FROM messages
  UNION
  SELECT receiver_id AS uid, richiesta_id
  FROM messages
) AS DistinctCodes
GROUP BY DistinctCodes.richiesta_id

Answer 2

簡化它：

SELECT sender_id as idutente, richiesta_id
FROM messages
WHERE sender_id IS NOT NULL
UNION
SELECT receiver_id, richiesta_id
FROM messages
WHERE receiver_id IS NOT NULL