Generating sequential numbers in multi-user saas application

Question

How do people generate auto_incrementing integers for a particular user in a typical saas application?

For example, the invoice numbers for all the invoices for a partic

Answer 1

Do you really want to generate the invoice IDs in an incremental format? Would this not open security holes (where in, if a user can guess the invoice number generation, they can change it in the request and may lead to information disclosure). I would ideally generate the numbers randomly (and keep track of used numbers). This prevents collisions as well (Chances of collision are reduced as the numbers are allocated randomly over a range).