sql - 哪个查询似乎有效？

Question

我想知道以下 2 个查询中哪个更快:-

Select s.*,
       sm.* 
  from tblStudent s
Inner Join (SELECT studentId,SUM(marks) As Sum
              from tblStudentsMarks  
           Group By studentId) as sm on s.StudentID = sm.StudentID;

...或:

Select s.studentId, 
       s.Name,
       SUM(Marks)
  From tblStudent s
Inner Join tblStudentsMarks sm On s.Studentid = sm.StudentId
  Group By s.studentId, s.Name;

编辑:-

第一个查询的查询估计:- http://img28.imageshack.us/img28/166/1stpicd.jpg

第二个查询的查询估计:- http://img245.imageshack.us/img245/5064/2ndpic.jpg

提前致谢:)

Answer 1

您可以同时运行它们并使用 execution plan比较它们。