Best Way To SELECT from database

tdnxxx444

Regarding maintainability / good practice issues vs speed I have a question regarding what is the best way to SELECT some data from a database.
I have the item_id of an item bought. I want to get a customer's billing information based on the item he bought. Should I do this with two queries or one using joins?

Here is my dbase schema:

customer_info

customer_id
name
cc_num
expdate

item_bought

item_id
customer_id

function getCustomerInfo($customer_id)
{
   $query = "SELECT customer_info.name, customer_info.cc_num, customer_info.expdate FROM customer_info WHERE customer_info.customer_id=$customer_id ";
   $result = mysql_query($query);
   $data = mysql_fetch_assoc($result);

   return $data;
}


function getCustomerInfoWithItemId($item_id)
{
   $query = "SELECT item_bought.customer_id FROM item_bought WHERE item_bought.item_id=$item_id ";
   $result = mysql_query($query);
   $data = mysql_fetch_assoc($result);

   $customer_data = getCustomerInfo($data['customer_id']);

   return $customer_data;
}

$data = getCustomerInfoWithItemId(400);

function getCustomerInfoWithItemId($item_id)
{
   $query = "SELECT customer_info.name, customer_info.cc_num, customer_info.expdate FROM customer_info, item_bought WHERE item_bought.item_id=$item_id ";
   $query .= "AND customer_info.customer_id = item_bought.customer_id ";
   $result = mysql_query($query);
   $data = mysql_fetch_assoc($result);

   return $data
}

$data = getCustomerInfoWithItemId(400);

thorpe

JOINS are your friend. the less queries the better basically.

tdnxxx444

Yea, there are less queries, but if I use method 1, I can reuse getCustomerInfo($customer_id) in other places.
However, with method 2, it maybe faster and less queries, but I will probably only be able to reuse the code in one instance.