Unique, unpredictable, 12 digit, integer id

Question

How would I go about generating this... I want to keep my primary key sequential and have a 12 digit unique pin generated for each new object added to the database.

Answer 1

You want two things

1. Uniqueness
2. Incremental

If you want both the things from same sequence you will run out of luck (literally) Uniqueness is guaranteed by having large sample space + random + check-unique. Which means, the actual number could be anywhere in between the sample space.

But if you want unique + incremental property, you are dividing sample space by 2. In 64 tries you would have reduced a 64 bit int sample space to 1 bit sample space.

Good luck !