Comprimeer rijen met nulls en duplicaten in enkele rijen

Select
   ID,
   AssnDate,
   AssnTxt,
   Max(IsNull(Sally,0)) AS Sally,
   Max(IsNull(Ted, 0)) As Ted,
   Max(IsNull(Bob, 0)) As Bob
From vwGrades
Group By
  ID,
  AssnDate,
  AssnTxt