I import a large table from our legacy system daily. It has a lot more data than I need, so I'm going to skip many of the columns. I'm also thinking
about normalizing the data some by splitting into two tables.

It's a customer table, and the columns I need are:

Billto#
Shipto#
and address info

The billto is the parent, and the shipto is the child. In many cases the billto is the same as the shipto. But a billto can also have multiple shipto's.
A billto cannot exist unless it is also a shipto.

I'll use this info generally for mailing. Sometimes I'll want to do mass mailings only to the Billtos, and sometimes I may want to do a mailing to all of the Shipto's belonging to a Billto.

I guess my question is:
Should I just leave everything in one table, or would I be better to split it into
2 tables with a one-to-many relationship? I'm leaning towards 1 table, but I'm not sure.

Thanks

It seems there might be advantages to having an Addresses table, with your main table having 1:M links to it on both the BillTo and ShipTo fields. From your description, it might be that ShipTo actually has M:M link to main table? This would require an intermediate table.

Here's a possible approach:

That's what I was looking for, but couldn't quite figure out.
Thanks a lot!