select iif(a.xyz is null, "D","I") from table as a;
If I view this query in Access, I correctly see D next to any field where xyz is null. If, however, I link this query to an Excel table, the D now flips to I when xyz is null. I have found that if I change the query to say a.xyz = "", the view in Access is now incorrect, but the data interpretation from Excel is now correct.
Does anyone have a better solution or more insight into the issue?