Question

imagine a database setup, where x customers can make y orders.
normally all customers would share one set of auto incremented order IDs.

• the first order of customer A has order id #1
• first order of customer B has order id #2.

i’d like to have individual sets of order IDs for each customer. it is important, that customers cannot see based on the id how many other customers have made orders.

• first order of customer A has order id #1
• second order of customer A has order id #2
• first order of customer B has order id #1

right now, the only way i can see would be to manually select the max value for the customer’s order number, add +1 and then insert it manually.

select max(customer_order_id) from orders where customer_id = X

how can i create this approach in a sense of data integrity and normalization? like having some kind of auto increment for the individual order ids of the customer?

create table customers
(
  id int auto_increment primary key, 
  name varchar(255)
);

create table orders
(
  id int auto_increment primary key, 
  customer_id int
  customer_order_id int 
  foo varchar
  bar varchar
);

Answer 1

Just make the order number the customer number followed by a sequence number. So if I’m customer 103985, my first order is 103985-0001, my second order is 103985-0002. Normalize the data — in an order, store the customer number and the sequence number separately. Combine them for display.