When you book one hotel room, or one record, you need to replace that record's last column value from blank to certain customer ID. According to the instruction, "The system you are writing does not interact with these numbers, rather it simply records them", so my solution is:
1) create a sample customer ID arry which contains something like"12345678", or "23456789", etc.
2) when doing booking, randomly select one ID from that ID array.
Is this ok?
Thanks.