带有内部连接的别名

Question

我有以下查询，其中 'ID' 的字段不明确，我知道我需要使用别名，但在第二个示例中使用别名时似乎做错了什么

SELECT * FROM 01users 

INNER JOIN 01modules ON 01modules.Modules_UserID = 01users.ID 

INNER JOIN 01articles ON 01modules.ID = 01articles.ModuleID

WHERE User =  '$user' AND ID = '$moduleid'

ORDER BY WeekID ASC

我按照一些在线示例进行操作，但在第二行出现错误。

SELECT t1.ID

FROM 01users AS t1

INNER JOIN 01modules ON 01modules.Modules_UserID = t1.ID 

INNER JOIN 01articles ON 01modules.ID = 01articles.ModuleID

WHERE User =  '$user' AND ID = '$moduleid'

ORDER BY WeekID ASC

有什么解决办法吗？

Answer 1

试试下面的查询

SELECT t1.ID
FROM 01users AS t1
INNER JOIN 01modules ON 01modules.Modules_UserID = t1.ID 
INNER JOIN 01articles ON 01modules.ID = 01articles.ModuleID
WHERE User =  '$user' AND t1.ID = '$moduleid'
ORDER BY WeekID ASC

您还需要在 where 子句中使用别名。

这一行

WHERE User =  '$user' AND ID = '$moduleid'

改成了这个

WHERE User =  '$user' AND t1.ID = '$moduleid'

Answer 2

学习使用 table 别名！

SELECT *
FROM 01users u INNER JOIN
     01modules m
     ON m.Modules_UserID = u.ID INNER JOIN
     01articles a
     ON m.ID = 01artacles.ModuleID
WHERE u.User =  '$user' AND m.ID = '$moduleid'
ORDER BY ?.WeekID ASC

您应该限定所有列引用，包括 WeekId -- 这就是 ? 的用途。

您还应该明确列出您想要的列，而不是使用 select *。

Answer 3

解决方法如下：

SELECT u.User, m.ID, a.Title, a.Topic, a.Text, a.WeekID, a.DatePosted, a.DateDue, a.TimePublished, a.File1, a.ID AS ArticleID
FROM 01users as u 
INNER JOIN 01modules AS m ON m.Modules_UserID = u.ID 
INNER JOIN 01articles AS a ON m.ID = a.ModuleID
WHERE User =  '$user' AND m.ID = '$moduleid'
ORDER BY WeekID ASC

带有内部连接的别名

Alias with inner joins

sql

alias

inner-join