Newbie here!

I have a workflow that retrieves BP variable from a Form that is filled out and then inserts some of that data into a SQL table.  I have multiple date columns in the SQL table and only a couple of them are filled in with variables from the From.  The other dates are to be added at a different time through a different WF process.  Those dates that are not yet added are being returned as 1900-01-01 in my SQL table.  I have tried setting the value for these date columns to %(DB.NULL) and that does not work - the 1900-01-01 is still input into the table.  I have also tried to EXCLUDE those date columns that are not filled in yet...and I'm still getting the 1900-01-01 in the table.

Also, the columns in my table are set to allow nulls

See pics of my WF showing data insert values and what I'm getting in added to my SQL table.

What am I doing wrong?