I suppose you are using the Multiple Database Server functionality were you are connected to a leading database and write back information to the Excel file? If so, please make sure that you use the Unique ID of the leading database as the unique ID for the Excel file. That means that you need to connect the ID of the Excel file to the database column of the leading database that contains the unique ID. Every time you print a card, CE will check if that record is available in the Excel file and depending on that result will update the field or insert a new record otherwise the MifareID column will be empty and you have probably defined this column as the PK of the Excel file, and in that case, the error message is correct because a PK field is not allowed to be null if it refers to a unique record.
Marcel Oosterhof Support Team
Simplicity means an easy to use interface even for complex solutions...
Ah ok. Yes I'm using two databases, one with a fixed number of records and an empty one (which is the Excel file) in which records are inserted for every record in the source db. The destination db will contain the read mifare ids
So if I understand you correctly, I could better use the same database for input (with a fixed number of records) as for output and update the values instead of inserting them with an automatically incrementing id. This database would then be the Excel file or a comma separated file.