Overwrite value in DB with a NULL using VBA - sql-server

Question

If cell.Value <> "" Then
uid = cell
lname = Left(Replace(Range(cell.Address).Offset(0, 1), "'", ""), 50)
fname = Replace(Range(cell.Address).Offset(0, 2), "'", "")
stat = Replace(Range(cell.Address).Offset(0, 3), "'", "")
role = Left(Replace(Range(cell.Address).Offset(0, 4), "'", ""), 50)
iqn = Replace(Range(cell.Address).Offset(0, 5), "'", "")
sdate = Format(Replace(Range(cell.Address).Offset(0, 6), "'", ""), "yyyy-mm-dd")
bdate = Format(Replace(Range(cell.Address).Offset(0, 7), "'", ""), "yyyy-mm-dd")
rodate = Format(Replace(Range(cell.Address).Offset(0, 8), "'", ""), "yyyy-mm-dd")
End If
hirereason = Replace(Range(cell.Address).Offset(0, 9), "'", "")
roreason = Replace(Range(cell.Address).Offset(0, 10), "'", "")
sql = "BEGIN TRAN IF EXISTS (SELECT * FROM " & TableName & " WITH (updlock, serializable)"
sql = sql & " WHERE UID = '" & uid & "')"
sql = sql & " BEGIN"
sql = sql & " UPDATE" & TableName
sql = sql & " SET LName='" & lname & "', FName='" & fname & "'"
sql = sql & ", Status='" & stat & "', Role='" & role & "'"
sql = sql & ", IQNRole='" & iqn & "', StartDate='" & sdate & "'"
sql = sql & ", BillableDate='" & bdate & "', RollOffDate='" & rodate & "'"
sql = sql & ", HireReason='" & hirereason & "', RollOffReason='" & roreason & "'"
sql = sql & " WHERE UID = '" & uid & "'"
sql = sql & " END"
sql = sql & " ELSE BEGIN"
sql = sql & " INSERT " & TableName & " (UID, LName, FName, Status, Role, IQNRole, StartDate"
sql = sql & ", BillableDate, RollOffDate, HireReason, RollOffReason)"
sql = sql & " VALUES('" & uid & "', '" & lname & "', '" & fname & "', '" & stat & "'"
sql = sql & ", '" & role & "', '" & iqn & "', '" & sdate & "', '" & bdate & "', '" & rodate & "'"
sql = sql & ", '" & hirereason & "', '" & roreason & "')"
sql = sql & " END COMMIT TRAN"
Cn.Execute (sql)
End If
I have some values and I'm formatting the date values which come is as string to date. If I run this as is it puts a default value for "" into the DB as 1900-1-1. I want the NULL values to actually stay in the DB and not be over-written. Furthermore I want them to update a cell with NULL if say it didn't use to be but now is.
I tried wrapping my value rodate in an IF statement and tried validating it against NULL, NOTHING, and EMPTY to say if it is one of these UPDATE DB with "NULL" but it doesn't do it. Date still comes out 1900-1-1. Any ideas?

Answer 1

Dim roDate
'...
'...
rodate = Trim(cell.Offset(0, 8).Value)
If len(rodate)=0 Then
rodate = null
else
rodate = "'" & Format(rodate, "yyyy-mm-dd") & "'"
end if
'....
'....
'note no single quote here around rodate
sql = sql & ", BillableDate='" & bdate & "', RollOffDate=" & rodate
'...
'...

Answer 2

I'm confused, not sure if I get this question right.
The only thing I understood from it is that you are struggling with saving a date as NULL in the database.
NULL and an empty string are not the same.
Try and see if this works:
dim vNull as variant
vNull = Null
if sDate = "" then
//Save vNull instead of Date
end if
I don't believe that you can capture NULL in a string datatype.
Edit
Perhaps stupid that I didn't think of this before, but instead of an empty string, can't you just put the string "NULL" in the query string?