MySQL custom primary key generator

Question

I have written an invoice module for our reservation system.

So when I create a new invoice, I automatically generate a primary key through MySQL.

However for th

Answer 1

You can make two fields in your, year and id.

Make one primary key on both fields, giving id the auto_increment option. For each unique value of year, id will be counting up. For example:

2012    1
2012    2
2012    3
2013    1

And you can concat them when selecting: SELECT CONCAT(year,id) AS primary FROM table

Inserting will be:

INSERT INTO table SET year = YEAR(NOW())

you don't have to specify id.