when i execute the query output i snot coming correctly

Question

 SELECT distinct r.rate as Rate,f.bthid as Batchid,CASE  WHEN r.rate = '1' THEN '100' WHEN r.rate = '2' THEN '75' WHEN r.rate = '3' THEN '50' WHEN r.rate = '4' THEN '25' ELSE '0' END AS Translated_Rate FROM bthfac AS f,batch AS b, faculty AS fa,facfeedback AS r where  month(b.examdate)= '9' and year(b.examdate)= '2011' and b.bthid=f.bthid and r.bfid = f.bfid and fa.facname = 'MADHAVAN'

when i  execute the above query  output as follows;

rate  Batchid Translated_Rate

 0  13         0

3  13       50

4  9       25

1  8     100

4  14     25

1  6    100

2  24     75

2  12    75

4  4     25

1 13    100

but in the above query, when i change the facname (facultyname) and execute the query,same output is coming for all the faculty.

what is the problem in my above sql server query please help me.

Regards,

Narasiman P.