MySQL ID按适当的系列

Question

We are building an invoice management app and need help/suggestions with the following...

1. Invoice should start with 1 and according to series like 1 2 3 4 5 6 7 8 not 1 3 4 7
2. It should start with 1 again each financial year for example it should start with 1 again in 2012
3. how to show all invoices older than febuary 2011 and newer than march 2010 means financial year

We want your suggestions to achieve this. thanks.

Answer 1

you need compound primary key. eg:

year int
invoice_id int

Answer 2

1. The incrementing ID is trivial in MySQL. A simple auto_Increment primary key column does the trick.
2. Having the number wrap back to 1 each year can't be done with vanilla SQL without triggers and/or client-side involvement.
3. The fiscal year business is more of a client-side issue. Simply store a "created on" timestamp with each record and then decide on the filtering rules in the client, then you simply do select ... where date_of_record between $start_of_period and $end_of_period .

Answer 3

Create the primary key as in heximal's answer. Then use this to insert a new id:

insert into my_table (id, year)
   values (
      coalesce (
      (
         select new_id = max(id) + 1
         from my_table
         where year = @year
      ), 1)
      , @year
   )