Question

比方说我下面有这个查询。

SELECT UserSub.Lastname 
FROM (
    SELECT UserId, Email, Firstname, Lastname as COL_1234 
    FROM Users
) 
as UsersSub;

这将导致错误

Error Code: 1054. Unknown column 'UsersSub.Lastname' in 'field list'

我知道它不起作用，因为子查询未返回列Lastname。当我将UsersSub.Lastname更改为UsersSub.COL_1234时，它可以正常工作。但是我需要一种基于别名检索原始列名的方法。子查询是由我无法更改的另一部分代码生成的，因此这对我没有影响。因为稍后需要在查询中添加where子句，并且需要在别名字段上进行搜索。因此，在即将发布的功能中，查询将如下所示。

SELECT UserSub.Lastname 
FROM (
    SELECT UserId, Email, Firstname, Lastname as COL_1234 
    FROM Users
) 
as UsersSub
WHERE UserSub.Lastname LIKE '%son';

Answer 1

我认为这会起作用：

SELECT u.Lastname
FROM (
    SELECT UserId, Email, Firstname, Lastname as COL_1234 
    FROM Users
) AS UsersSub
LEFT JOIN ON Users AS u WHERE UsersSub.UserId = u.UserId
WHERE UserSub.Lastname LIKE '%son';

Answer 2

尝试一下，对我来说很好

SELECT UserSub.Lastname 
FROM (
    SELECT UserId, Email, Firstname, Lastname, Lastname as COL_1234 
    FROM Users
) 
as UsersSub
WHERE UserSub.Lastname LIKE '%son';

获取别名的基础列名称

2 个答案: