Trouble With An Insert Into/select Statement

I have several tables in a database which I always want to update with information from one table with new records (containing contact and demographical information). The setup is something like this:

NewRecordsTable: fn, ln, streetadd, city, emailadd, phonenumber, gender, birthdate

ContactTable: ID(primarykey), fn, ln, streetadd, city, state, zip, phonenumber, email

DemographicTable: ID(linked to primary key ID in Contact table), birthdate, gender


I want to update the ContactTable and DemographicTable with information from the NewRecords Table. What I have done so far is set the identity insert for the ContactTable to on, then inserted the fn, ln, streetadd, email, etc. from the NewTable. This works fine.

I then try to insert ID, birthdate and gender into the DemographicTable where NewRecordsTable.fn=ContactTable.fn AND NRT.ln=CT.ln AND NRT.streetadd=CT.streetadd AND NRT.emailadd=CT.emailadd - This mostly works, but the records which have NULL values any of those fields don't get inserted.

What I really want is to insert the records that have matching email addresses OR matching fn, ln, streetadd combos, but I can't figure out how to get that SELECT/WHERE statement to work.

The problem that underlies this is that I want to insert the ID values from the ContactTable into the DemographicTable, but the only way I can see to make them match properly is by matching the email addresses or fn, ln, streetadd combos from the NewRecordsTable to the ContactTable (all of the email addresses in our NewRecordsTable are unique, unless the person doesn't have an email address, in which case we make sure they have a unique fn, ln, streetadd combo)

Any help would be appreciated,
Thank you!!