MySql：從同一表的三個不同列中提取不同的條目

Question

我有一個表稱為deals存儲client_id1 ， client_id2 ， client_id3 。

這些ID對應於具有clientName和client_id字段的clients表。

如何創建一個名稱由字符串組成的字符串數組，該ID的ID在表交易的三列中的任何一列中。

Answer 1

SELECT GROUP_CONCAT(Client) FROM (
 SELECT clientName as Client 
 FROM deals JOIN clients
 ON deals.client_id1 = clients.client_id
UNION ALL
 SELECT clientName as Client 
 FROM deals JOIN clients
 ON deals.client_id2 = clients.client_id
UNION ALL
 SELECT clientName as Client 
 FROM deals JOIN clients
 ON deals.client_id3 = clients.client_id)
GROUP BY Client

說明：

從一張桌子獲得客戶：

 SELECT clientName as Client 
 FROM deals JOIN clients
 ON deals.client_id1 = clients.client_id

工會也會從其他表中獲取它們

 SELECT clientName as Client 
 FROM deals JOIN clients
 ON deals.client_id1 = clients.client_id
UNION ALL
 SELECT clientName as Client 
 FROM deals JOIN clients
 ON deals.client_id2 = clients.client_id
UNION ALL
 SELECT clientName as Client 
 FROM deals JOIN clients
 ON deals.client_id3 = clients.client_id)

現在，要獲取逗號分隔字符串，請使用GROUP_CONCAT進行此客戶端（php）或讓MySQL服務器完成：

SELECT GROUP_CONCAT(Client) FROM (
 SELECT clientName as Client 
 FROM deals JOIN clients
 ON deals.client_id1 = clients.client_id
UNION ALL
 SELECT clientName as Client 
 FROM deals JOIN clients
 ON deals.client_id2 = clients.client_id
UNION ALL
 SELECT clientName as Client 
 FROM deals JOIN clients
 ON deals.client_id3 = clients.client_id)
GROUP BY Client