從SQL Join Query重命名返回的值

Question

可以說我們有以下查詢

SELECT b.user_name, c.user_name, msg 
FROM user_messages a
JOIN users b ON b.user_id = a.user_from 
JOIN users c ON c.user_id = a.user_to 
WHERE a.user_from = 'ds4EpcrmUt' 
OR a.user_to = 'ds4EpcrmUt'

從NodeJS查詢時，我只會收到一個user_names，因為兩個返回的值都具有相同的名稱。

有沒有辦法重命名他們的返回值，如下所示？

b.user_name = user_from
c.user_name = user_to

Answer 1

試試以下 -

SELECT b.user_name as user_from, c.user_name as user_to, msg 
FROM user_messages a
JOIN users b ON b.user_id = a.user_from 
JOIN users c ON c.user_id = a.user_to 
WHERE a.user_from = 'ds4EpcrmUt' 
OR a.user_to = 'ds4EpcrmUt'

Answer 2

當您引用相同的列名時，您需要不同的列別名，例如user_name1和user_name1或您喜歡的列名別名：

SELECT b.user_name user_name1, c.user_name user_name2, msg 
FROM user_messages a
JOIN users b ON b.user_id = a.user_from 
JOIN users c ON c.user_id = a.user_to 
WHERE a.user_from = 'ds4EpcrmUt' 
OR a.user_to = 'ds4EpcrmUt'

Answer 3

SELECT b.user_name as user_from, c.user_name as user_to, msg 
FROM user_messages a
JOIN users b ON b.user_id = a.user_from 
JOIN users c ON c.user_id = a.user_to 
WHERE a.user_from = 'ds4EpcrmUt' 
OR a.user_to = 'ds4EpcrmUt'