How to generate unique id in MySQL?

Question

I\'m programming a script using PHP and MySQL and I want to get a unique id (consisting of a string: capitals and small letters with numbers) like: gHYtUUi5b.

Answer 1

How you generate the unique_ids is a useful question - but you seem to be making a counter productive assumption about when you generate them!

My point is that you do not need to generate these unique id's at the time of creating your rows, because they are essentially independent of the data being inserted.

What I do is pre-generate unique id's for future use, that way I can take my own sweet time and absolutely guarantee they are unique, and there's no processing to be done at the time of the insert.

For example I have an orders table with order_id in it. This id is generated on the fly when the user enters the order, incrementally 1,2,3 etc forever. The user does not need to see this internal id.

Then I have another table - unique_ids with (order_id, unique_id). I have a routine that runs every night which pre-loads this table with enough unique_id rows to more than cover the orders that might be inserted in the next 24 hours. (If I ever get 10000 orders in one day I'll have a problem - but that would be a good problem to have!)

This approach guarantees uniqueness and takes any processing load away from the insert transaction and into the batch routine, where it does not affect the user.