Error: "No column name was specified for column 1 of 'SOURCE'" in SQL Server Merge statement

when I was working with Merge statement with SQL Server 2008 then while writing this I got this error and after couple of min i got the issues 

Declare

      @Id         Int = 10,

      @Name       Varchar(20) = 'Kesharwani',

      @Salary     Int = 30000

          

MERGE INTO [Temp] as TARGET

      USING (SELECT @Id,@Name,@Salary) AS

SOURCE ON TARGET.empId = SOURCE.empId

      WHEN MATCHED THEN

            UPDATE SET Name=SOURCE.Name, Salary =SOURCE.Salary

      WHEN NOT MATCHED THEN

            INSERT (empId,Name,Salary)

VALUES (SOURCE.empId,SOURCE.Name,SOURCE.Salary);

While running above query sometime I got this error: No column name was specified for column 1 of 'SOURCE'.

The problem in the above query the alias name not there on the columns in Select statement, to resolve this error above query can be written in following way

Declare

      @Id         Int = 10,

      @Name       Varchar(20) = 'Kesharwani',

      @Salary     Int = 30000

          

MERGE INTO [Temp] as TARGET

      USING (SELECT @Id AS empId,@Name AS Name,@Salary AS Salary) AS

SOURCE ON TARGET.empId = SOURCE.empId

      WHEN MATCHED THEN

            UPDATE SET Name=SOURCE.Name, Salary =SOURCE.Salary

      WHEN NOT MATCHED THEN

            INSERT (empId,Name,Salary)

VALUES (SOURCE.empId,SOURCE.Name,SOURCE.Salary);