Subtract count results of one table from another?

[Oceankoi]

What I am trying to accomplish is to take one tables count results, group it by item name then subtract those results from a second grouped table. Then return the item name with the new count results.

 

What I have so far:

 

function doLoadItem($id) {

	$sql = sprintf("SELECT *, count(item_name) as amount 
	FROM item_table 1
	WHERE user_id = $id
	GROUP BY item_name");

	$sql2 = sprintf("SELECT *, count(item_name) as amount 
	FROM item_table 2
	WHERE user_id = $id
	GROUP BY item_name");

	$a = mysql_query($sql);
	$b = mysql_query($sql2);
	$result = $b-$a;
	// Return result
	return $result;
}

 

This dose subtract my count results but its just one number. So I dont think its returning an array anymore.

[fenway]

This:

 

$result = $b-$a;

 

Is completely undefined for result sets! It sounds like you simply want item_name, COUNT(table2-table1) as the final output -- you could do this with derived tables and have sql do it all.