tico:
So I can't change the customer I.D. in ZC. I now understand that. I will have to cross reference my customer I.D.'S with the ones that ZC cart gives.
Zencart's "ID system" is a principle applied to many data-sets and is the KEY mechanism used to create internal relationships between commonly used bits of data acros the database. It is not something that has relevance from the user's (website visitor's) point of view.
This system uses the AUTO-INCREMENT function common to all modern databases, and it simply increments the value by one integer as each new data record is added.
While technically possible to "synchronise" this internal ID with the unique Id you give your customers, the administration of this would be a nightmare, because you would need to know every instance where the internal customer ID is referenced, and make sure that all these ID's are not only unique, but they EXACTLY match up... One tiny error and you will get the database delivering results of some database queries, of information belonging to "Mr Smith", being served up to "Mr Jones".