Question

Here’s my problem: I’m making a crafting system for a game, and I already have my database filled with information for resources required to craft items.

Here are what my relevant tables look like:

table #edible_resources
(edible_resource_id, edible_resource_name, hunger_points, degeneration_id)

table #edible_ground
(id, resource, amount, location)

table #req_crafting_edible
(req_crafting_edible_id, edible_resource_id, req_resource_amount, created_item_id)

table #items
(item_id, item_name, degeneration_id, is_grounded, is_stackable, can_equip, can_edit)

What I want to do is -only- echo out the craftable item’s name if, and only if -all- required resources (and their required amounts) are on the ground in the location of the character.

I have a query that comes close:

SELECT items.item_name, items.item_id FROM items
INNER JOIN req_crafting_edible
ON req_crafting_edible.created_item_id = items.item_id
INNER JOIN edible_ground
ON edible_ground.resource = req_crafting_edible.edible_resource_id
AND edible_ground.amount >= req_crafting_edible.req_resource_amount
WHERE edible_ground.location = $current_location
GROUP BY items.item_name
ORDER BY items.item_name

But this shows me craftable items regardless if I have ALL the required items in the area. It shows me items as long as I have -one- of their required resources.

Is there a way to only show the name of a craftable item only if I have -all- the required resources (and their amounts) in edible_ground where location = $current_location?

For more information on what I’ve tried:

$get_char = mysql_query("SELECT current_char FROM accounts WHERE account_id ='".$_SESSION['user_id']."'");
$current_char = mysql_result($get_char, 0, 'current_char');

$get_loc = mysql_query("SELECT current_location FROM characters WHERE character_id = $current_char");
$current_location = mysql_result($get_loc, 0, 'current_location');

//---------------------------------------------------------------COOKED FOOD
$get_food = mysql_query("SELECT items.item_name, items.item_id FROM items
INNER JOIN req_crafting_edible
ON req_crafting_edible.created_item_id = items.item_id
INNER JOIN edible_ground
ON edible_ground.resource = req_crafting_edible.edible_resource_id
AND edible_ground.amount >= req_crafting_edible.req_resource_amount
WHERE edible_ground.location = $current_location
GROUP BY items.item_name
ORDER BY items.item_name");
while ($food = mysql_fetch_array($get_food)){
  echo $food['item_name'].'<br>';
}

This returns:

• Baked Fish
• Charred Fish
• Fish Soup
• Glazed Berry
• Cake
• Grilled Fish
• Sashimi
• Seafood Soup
• Sushi
• Udon

On the ground:

• 1 fish
• 1 honey

Even though fish soup, berry cake, udon etc needs much more than just the one fish that’s in the area.

Can anyone help me figure this out? I’d be forever grateful; I’ve spent a few days already trying to myself. Please?

And before anyone says anything, I know I need to start using mysqli; unfortunately I didn’t even realize it existed when I started to make the game (and learn PHP at the same time months ago), so I’ll have to painfully go back and change it all in an update.

Answer 1

You want a HAVING clause to check the count of the records you are grouping through the INNER JOINs.

HAVING count(*) = (
  SELECT count(*)
    FROM req_crafting_edible
    WHERE req_crafting_edible.created_item_id = items.item_id
)

Edit:

So basically you need to know two pieces of information:

• How many different resources are required
• Do each of those resources have the required amounts

The first is solved by the sub query above.

Your query as-is satisfies the second point but only for 1 resource.

HAVING basically does some special magic on your group clause. HAVING count(*) means there are X records being grouped together. Because of how the join works, you will have 1 item.name for each resource. The sub select gives you the count of how many different resources, and therefore grouped records, are needed for that item. Comparing that sub query with the count(*) of the grouping ensures you have all the needed resources.

And here is the final query, modifying your code above:

SELECT items.item_name, items.item_id
  FROM items
    INNER JOIN req_crafting_edible
      ON req_crafting_edible.created_item_id = items.item_id
    INNER JOIN edible_ground
      ON edible_ground.resource = req_crafting_edible.edible_resource_id
        AND edible_ground.amount >= req_crafting_edible.req_resource_amount
  WHERE edible_ground.location = $current_location
  GROUP BY items.item_name
  HAVING count(*) = (
    SELECT count(*)
      FROM req_crafting_edible
      WHERE req_crafting_edible.created_item_id = items.item_id
  )
  ORDER BY items.item_name