I'm looking to generate a random number and issue it to a table in a database for a particular user_id. The catch is, the same number can't be used twice. There's a million ways to do this, but I'm hoping someone very keen on algorithms has a clever way of solving the problem in an elegant solution in that the following criteria is met:
1) The least amount of queries to the database are made. 2) The least amount of crawling through a data structure in memory is made.
Essentially the idea is to do the following
1) Create a random number from 0 to 9999999
2) Check the database to see if the number exists
2) Query the database for all numbers
3) See if the returned result matches whatever came from the db
4) If it matches, repeat step 1, if not, problem is solved.