Displaying entries with the same ID from the database - php

Question

I have a script that allows an admin to view orders that customers have made, where they can decide to view the order details or delete the order. A user can order 1 or more items, for which entries in the database are created with the same order_id, but with different product_id's. When I display my orders these duplicate entries show up, however I only want 1 entry for every order_id. Below is my function
function viewOrdersAdmin(){
//This block grabs the orders
$order_list = "";
//Selecting all the orders in the table from that member
$sql = mysql_query("SELECT * FROM `transactions`") or die(mysql_error());
while ($transactions = mysql_fetch_array($sql)) {
//creating variables from the information
$order_id = $transactions["order_id"];
$mem_id = $transactions["mem_id"];
$order_details = mysql_query("SELECT * FROM `transactionDetails` WHERE `order_id` = $order_id") or die(mysql_error());
$orderDetailsCount = mysql_num_rows($order_details);
while ($row = mysql_fetch_array($order_details)) {
//creating variables from the information
$order_product_id = $row["Product_ID"];
$member_details = mysql_query("SELECT * FROM `members` WHERE `mem_id` = $mem_id") or die(mysql_error());
$memberDetailsCount = mysql_num_rows($member_details);
while ($row2 = mysql_fetch_array($member_details)) {
//creating variables from the information
$order_mem_fname = $row2["mem_first_name"];
$order_mem_lname = $row2["mem_last_name"];
$order_list .= "Order ID:$order_id - Customer Name: $order_mem_fname $order_mem_lname <a href='manage_order.php?orderid=$order_id'>View</a> • <a href='manage_orders.php?deleteid=$order_id'>Delete</a><br/>";
}
}
}
if (count($orderDetailsCount) == 0) {
$order_list = "You have no orders to display";
}
print_r($order_list);
}

Answer 1

SELECT *
FROM transactions
GROUP BY order_id