Question

If I am building a multi-shop e-commerce solution and want the orders table to maintain a shop based sequential ID, what is the best way of doing this?

For instance imagine these order IDs in sequence: –

UK0001  
UK0002  
UK0003  
DE0001  
UK0004  
DE0002  

etc.

1. through grouped PK ID MySQL / MyISAM

   • MySQL will manage this automatically if a country field and
     an auto incrementing ID field are
     used. But MyISAM has some inherent
     problems such as table locking and
     this feature seems like it’s feature
     that is only available in MyISAM so
     moving database engine would not be
     possible with this solution.

2. Programmatically. Let’s say we have
   two fields: order_id (global auto
   inc PK column managed by DB),
   order_number (country specific
   sequential ID field maintained
   through code) and the table also has
   a shop_id column to associate orders
   to shops.

So – after the new order record has been created and the DB engine has assigned an ID to the new record, and the newly created order ID has been retrieved in code as variable $newID

select order_number+1 as new_order_number from orders where order_id < $newID and shop_id = UK order by order_id desc limit 1

(this is pseudo code / sql btw)

Questions:

1. is this a feasible solution? Or is there a better more efficient way to do this?

2. When the table has 1 million + records in it, will the additional query overhead per order submission cause problems, or not?

3. It seems there’d be a chance of order_number clashes if two orders are placed for the same country and they get processed simultaneously. If this a possibility? if so, is there a way of protecting against it? (perhaps a unique index and a transaction?)

Look forward to your help!

Thanks

Answer 1

Yes you are definitely on the right track. Set the ORDER ID field as UNIQUE and do the exact same thing you were trying to do. Add a catch statement where if it is not added because of the UNIQUE error, then try to insert it again with the same statement to ensure that the ORDER ID is never inserted with the same ID at the same time.