Why does MySQL return duplicate information in the returned JOIN array? - sql

Question

I'm wondering if I'm doing something wrong, or if this is just a quirk in how everything is processed in MySQL. Here's the setup: (I can't seem to find this exact topic anywhere else)
I have two tables order and menu.
menu has an 'id' (for the item), an 'item' and three prices ('prc1' 'prc2' 'prc3') in each row.
menu +----+----------+------+------+------+
|'id'| 'item' |'prc1'|'prc2'|'prc3'|
+----+----------+------+------+------+
| 1 | 'tshirt' | 3.00 | 4.50 | 4.00 |
| 2 | 'socks' | 1.00 | 2.50 | 2.00 |
+----+----------+------+------+------+
order also has an item id to match against the order menu, ('i_id'), and an integer I use for filtering the prices later in php ('prc_id').
order +------+--------+
|'i_id'|'prc_id'|
+--------+------+
| 1 | 1 | # i_id matches id - tshirt and informs to use prc1
| 2 | 3 | # i_id matchis id - socks and uses prc3
+--------+------+
I use JOIN to match the orders up to the items
"SELECT order.prc_id, menu.item, menu.prc1, menu.prc2, menu.prc3
FROM order
LEFT JOIN menu
ON order.i_id = menu.id"
I then get the result back, and initially to make sure everything panned out, I printed the array:
$result = mysql_query($query)
while($row = mysql_fetch_array($result))
{
print_r($row);
}
This is the array I get back (obviously dummy info for the initial tests):
Array
(
[0] => 1 [prc_id] => 1 #the value (1) for 'prc_id' is given twice
[1] => tshirt [item] => tshirt #the value (tshirt) for 'item' is given twice
[2] => 3.00 [prc1] => 3.00 #the value (3.00) for 'prc1' is given twice
[3] => 4.50 [prc2] => 4.50 #etc
[4] => 4.00 [prc3] => 4.00
[0] => 3 [prc_id] => 3
[1] => socks [item] => socks
[2] => 1.00 [prc1] => 1.00
[3] => 2.50 [prc2] => 2.50
[4] => 2.00 [prc3] => 2.00
)
So my question(finally, right? xD)... Why is duplicate data sent back in the array response?
Have I done something wrong? Am I overlooking something?
It's not a huge issue, it doesn't affect my end result, I'd just like to be as precise as possible.
Thank you for your time. :)

Answer 1

If think this is a PHP print_r() problem.
print_r() return a numeric representation and the second the named store row.
EDIT:
Try your query with the Database Query Tool then you will see the original result.

Answer 2

SELECT order.prc_id, menu.item, menu.prc1, menu.prc2, menu.prc3
FROM order
LEFT JOIN menu
ON order.i_id = menu.id
It looks like you are joining based on the item_id in order and id of menu, while you should be doing based on (if I understand correctly) the item_id of menu.
Something like:
SELECT order.prc_id, menu.item, menu.prc1, menu.prc2, menu.prc3
FROM order
LEFT JOIN menu
ON order.i_id = menu.item_id