declare @testKey table (testId int, questionId int, answer varchar(1))
Insert Into @testKey
Select 1, 1, 'A'
Union All Select 1, 2, 'B'
Union All Select 1, 3, 'A'

declare @studentAnswers table (studentId int, testId int, questionId int, answer varchar(1))
Insert Into @studentAnswers
Select 1, 1, 1, 'A'
Union All Select 1, 1, 2, 'B'
Union All Select 1, 1, 3, 'C'
Union All Select 2, 1, 1, 'B'
Union All Select 2, 1, 2, 'C'
Union All Select 2, 1, 3, 'B'
Union All Select 3, 1, 1, 'A'
Union All Select 3, 1, 2, 'B'
Union All Select 3, 1, 3, 'A'


	Select 
		A.StudentId, 
		A.testId, 
		QCnt = count(*),
		Correct = sum(case when A.answer = B.answer then 1 else 0 end),
		Grade = convert(money,sum(case when A.answer = B.answer then 1 else 0 end))/convert(money,count(*))*100
	From @studentAnswers as A
	Left Join @testKey as B
	On A.testId = B.testId
	and A.questionId = B.questionId
	Group By A.StudentId, A.TestId