how to use average in sql

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i have a table Rating in my project in which i have attribute Teacher_Id (int),Student_Id(int),Rating(int),Date(DateTime);
Teachers will rate their Student , now i want to select id of those student which have highest Rating but i have a problem if a teacher rate a student1 "4" and two teacher rate student2 "2" and "2" thus both have same ratings. I have a table name best student now this i have a problem to how to find the average of student and select best student id based on ratings.

Posted 19-Feb-13 3:34am

jackson kumar

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Kschuler 19-Feb-13 9:37am

So in that scenario, which student SHOULD be considered the best?

Sandeep Mewara 19-Feb-13 9:41am

Not clear.

Kschuler 19-Feb-13 10:02am

I know, that's why I asked. :)

Sandeep Mewara 19-Feb-13 10:28am

Oops! Sorry, pressed the wrong button.

My question is for OP.

ZurdoDev 19-Feb-13 10:06am

For average, just use AVG(). For example, SELECT AVG(studentscores) AS averagescore, studentid FROM sometable GROUP BY studentids

3 solutions

Solution 1

I won't do the work for you, but I'll give you a push in the right direction:

You can get the averages for each student in conjunction with a GROUP BY clause.

Further hint: if the possibility exists for a student to be listed but as yet unrated by one or more instructors, you need a mechanism to handle this, depending upon the default value of unrated student entries.

Posted 19-Feb-13 4:09am

W∴ Balboos, GHB

Solution 3

Hi Jackson ,

Please find the below query .

it will help to know about average in SQL server.

SQL

select Name,SUM(marks) as Sum ,AVG(marks) as Avegage from sa  Group By Name

Posted 19-Feb-13 18:10pm

Arul R Ece

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Maciej Los · Accepted Answer · 2013-02-19T08:43:00

if a teacher rate a student1 "4" and two teacher rate student2 "2" and "2" thus both have same ratings

How is it possible???

Try below query:

SQL

--Teacher_Id (int),Student_Id(int),Rating(int),Date(DateTime);

DECLARE @tt TABLE ([Teacher_Id] INT, [Student_Id] INT, [Rating] INT, [Date] DATETIME)

INSERT INTO @tt ([Teacher_Id], [Student_Id], [Rating], [Date])
VALUES(1,1,2,'2013-01-02')
INSERT INTO @tt ([Teacher_Id], [Student_Id], [Rating], [Date])
VALUES(1,1,2,'2013-01-03')
INSERT INTO @tt ([Teacher_Id], [Student_Id], [Rating], [Date])
VALUES(1,2,4,'2013-01-04')
INSERT INTO @tt ([Teacher_Id], [Student_Id], [Rating], [Date])
VALUES(1,3,5,'2013-01-05')
INSERT INTO @tt ([Teacher_Id], [Student_Id], [Rating], [Date])
VALUES(1,3,1,'2013-01-06')
INSERT INTO @tt ([Teacher_Id], [Student_Id], [Rating], [Date])
VALUES(1,4,4,'2013-01-07')
INSERT INTO @tt ([Teacher_Id], [Student_Id], [Rating], [Date])
VALUES(1,4,4,'2013-01-08')


SELECT  [Student_Id], [Rating]
FROM @tt

SELECT  [Student_Id], AVG([Rating]) AS AVERAGE
FROM @tt
GROUP BY [Student_Id]

Results:
1. query

Student_Id	Rating
1		2
1		2
2		4
3		5
3		1
4		4
4		4

2. query

Student_Id	Average
1		2
2		4
3		3
4		4