Question

I have a table that stores orders.
id (auto increment) an oid (not auto incremented) and then the order details.
some orders can have multiple entries, this is why i have an ID and an Oid(order id)
so if you order 3 xwidgets and 4Zwidgets they go under the same OID

I am using the following code to assign the next OID number and am wondering if this is the best way:

$maxquery = mysql_query("SELECT MAX(oid) FROM ordr") or die(mysql_error());
$maxresult = mysql_fetch_array($maxquery);
$maxid = $maxresult['MAX(oid)'];
$oid = $maxid + 1; -- this gives me a new OID for the next entry since i can not auto increment this column

Answer 1

You probably want to use auto-increment columns. This will let you insert the data, and MySQL will pick an index for you. You’ll need to denormalize your data to do this though.

You’ll want two tables: orders and order_items, where:

orders
------
order_id
[any other columns]


order_items
-----------
item_id
order_id
[any other columns]

Insert the order into the orders table with a NULL order_id and record the order_id that MySQL sets. Now insert the order_item using the order_id you have, and let it auto-generate the item_id.

This way, MySQL will generate the numbers, so you don’t need to worry about two orders trying to use the same order ID. Also, any order information won’t be duplicated for each item in the order.