This make-table query produces the desired result:

Select FieldA,
       Max(SomeFloat) As SomeFloat
Into NewTable
From OldTable
Group by FieldA, FieldB
This gives the correct data --> Select * from NewTable

In SSMS, the columns for NewTable shown are:

FieldA Number
FieldB Character
SomeFloat Null <-- Datatype "Null"

And NewTable in Design View doesn't even show the SomeFloat field.

The work-around is to explicitly type column 3 as --> Cast(Max(SomeFloat) As Float) As SomeFloat

Then things look OK.

I don't understand why the table holds data (the Select * from Newtable works)
Yet the column that holds the Domain data doesn't even show up in design view.

Any ideas anyone?