如何顯示多行數據在一排所有唯一ID

Question

我有以下查詢其選擇不同源的語言，但我想表明它在一排

SELECT msg_id, 
    CASE WHEN source=0 THEN language_name END AS 'language1', 
    CASE WHEN source=2 THEN language_name END AS 'language2', 
    CASE WHEN source=1 THEN language_name END AS 'language3' 
    FROM languages 
    WHERE msg_id=90491 


    msg_id language1 language2 language3 
    90491 Marathi  NULL  NULL 
    90491 NULL  NULL  English 
    90491 NULL  Hindi  NULL 

但我想結果爲

msg_id language1 language2 language3 
    90491 Marathi  Hindi  English 

我如何得到它

Answer 1

您可以使用INNER選擇查詢，如：

SELECT l.msg_id, 
(SELECT language_name FROM languages WHERE msg_id = l.msg_id AND source = 0) AS 'language1', 
(SELECT language_name FROM languages WHERE msg_id = l.msg_id AND source = 1) AS 'language2', 
(SELECT language_name FROM languages WHERE msg_id = l.msg_id AND source = 2) AS 'language3' 
FROM languages l 
WHERE l.msg_id=90491 

此查詢假定表中只有一個記錄，每個msg_id和source組合。