从SQL Join Query重命名返回的值

Question

可以说我们有以下查询

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'

从NodeJS查询时，我只会收到一个user_names，因为两个返回的值都具有相同的名称。

有没有办法重命名他们的返回值，如下所示？

b.user_name = user_from
c.user_name = user_to

Answer 1

试试以下 -

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

当您引用相同的列名时，您需要不同的列别名，例如user_name1和user_name1或您喜欢的列名别名：

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'