How to import a large database, where records do not always have lastnames?

How to import a large database, where records do not always have lastnames?

We have a database of 30,000 records.  Many do not have last names.  Some do not have company names.  Some do not have emails.  There is no piece of data that all records have.

What to do?

Questions:
1. What would other users suggest as a strategy?  This must be a very common issue.
2. Does Zoho CRM allow records to be indexed by something other than the last name?
3. Why not create a new, numerical column and index the records by this?