Coping data from one application to another and keeping parent/child links

I build kind of a makeshift ERP system almost 10 years ago for a company I used to work for that ended up consisting of 4 different applications, each with multiple tables, and they are all connected via table and cross-application relationships. It was built that way because A) I was just teaching myself QuickBase at the time so I didn't really know any better, and B) I started out with just one small piece and my managers loved it so much they kept asking for new pieces, so I continued to add new branches and tying back into what was already built while the parts that were complete were being utilized on a daily bases. Recently I started working on a streamlined version of what I built back then as a new, single application, cutting all the unnecessary tables and changing up many of the fields that were in use to better options available now.

My question is this, what is the best way to copy the data from the old version to the new version, and keeping the parent/child links on the tables that are hold overs from the previous version? I know some of the new fields won't copy necessarily.

Or, now that I am thinking about it, would I have been better off maybe copying the existing applications and then merging those tables into one app and just making the changes to those tables versus creating all new?

Any advise is much appreciated.

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Chris Swirtz
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