MySql 5.6列级查询

Question

我在MySQL 5.6中尝试以下SQL：

select Test=1 from ALL_FILES_INFO; 

但是我收到了一个错误。

错误代码：1054。“字段列表”中的未知列“测试”

这是像这样的事情

Select Name,
       Amount=(select Amount from EmployeeAmount where EmployeeName=Name)
 from Employee;

相同的代码在Microsoft SQL Server中正常运行。

Answer 1

SQL Server有一种说明列别名的替代方法，据我所知，这可以完全相同，并且可以在MySQL和SQL Server上运行;

SELECT 1 AS Test from ALL_FILES_INFO; 

SQLFiddle for SQL Server
SQLFiddle for MySQL

Answer 2

加入表格比使用相关子查询更好：

SELECT Employee.Name, EmployeeAmount.Amount
FROM   Employee
  JOIN EmployeeAmount ON EmployeeAmount.EmployeeName = Employee.Name