Creation of view with case when statement

Question

Please refer to my example below for clearer understanding of what i'm doing.

Example:

Create View v AS
Select T.*, S.Name, Case When T.TESTDATE = S.STUDYDATE
Then 'Yes' else 'No' END AS TakenTest
From Test T, Student S
Where T.TESTPAPERID = '12345'
And T.StudentNo = S.StudentNo;

It create the view successfully. However, it populate duplicate rows with same values like:

TESTPAPERID      StudentNo      Name     TakenTest
12345            6437           John     Yes
12345            6437           John     No

How can i resolve it as i already define that if T.TESTDATE = S.STUDYDATE then show yes. Otherwise no. And not populating the same values out.

Thanks

Answer 1

To have only one row, use this:

MAX(Case When T.TESTDATE = S.STUDYDATE Then 'Yes' else 'No' END)
...
GROUP BY <all other columns, which you haven't shown>

Also, this part is poorly coded:

T.TESTPAPERID = (Select TESTPAPERID From Student Where TESTPAPERID='12345')

because it is IDENTICAL to:

T.TESTPAPERID = '12345'