Pure SQL vs PHP While Loop To Perform an Update Faster - php

Question

I'm currently working on a system to managed my Magic The Gathering collection. I've written a script to update pricing for all the cards utilizing a WHILE loop to do the main update but it takes about 9 hours to update all 28,000 rows on my i5 laptop. I have a feeling the same thing can be accomplished without the While loop using a MySQL query and it would be faster.
My script starts off by creating a temporary table with the same structure as my main inventory table, and then copies new prices into the the temporary table via a csv file. I then use a While loop to compare the cards in temp table to the inventory table via card_name and card_set to do the update.
My question is, would a pure mysql query be faster than using the while loop, and can you help me construct it? Any help would be much appreciated. Here is my code.
<?php
set_time_limit(0);
echo "Prices Are Updating. This can Take Up To 8 Hours or More";
include('db_connection.php');
mysql_query("CREATE TABLE price_table LIKE inventory;");
//Upload Data
mysql_query("LOAD DATA INFILE 'c:/xampp/htdocs/mtgtradedesig/price_update/priceupdate.csv'
INTO TABLE price_table FIELDS TERMINATED BY ',' ENCLOSED BY '\"' (id, card_name, card_set, price)");
echo mysql_error();
//UPDATE PRICING
//SELECT all from table named price update
$sql_price_table = "SELECT * FROM price_table";
$prices = mysql_query($sql_price_table);
//Start While Loop to update prices. Do this by putting everything from price table into an array and one entry at a time match the array value to a value in inventory and update.
while($cards = mysql_fetch_assoc($prices)){
$card_name = mysql_real_escape_string($cards['card_name']);
$card_set = mysql_real_escape_string($cards['card_set']);
$card_price = $cards['price'];
$foil_price = $cards['price'] * 2;
//Update prices for non-foil in temp_inventory
mysql_query("UPDATE inventory SET price='$card_price' WHERE card_name='$card_name' AND card_set='$card_set' and foil ='0'");
//Update prices for foil in temp_inventory
mysql_query("UPDATE inventory SET price='$foil_price' WHERE card_name='$card_name' AND card_set='$card_set' and foil ='1'");
}
mysql_query("DROP TABLE price_table");
unlink('c:/xampp/htdocs/mtgtradedesign/price_update/priceupdate.csv');
header("Location: http://localhost/mtgtradedesign/index.php");
?>

Answer 1

The easiest remedy is to perform a join between the tables, and update all rows at once. You will then only need to run two queries, one for foil and one for non foil. You can get it done to one but that gets more complicated.
UPDATE inventory i
JOIN price_table pt
ON (i.card_name = pt.card_name AND i.card_set = pt.card_set)
SET i.price = pt.card_price WHERE foil = 0;
Didn't actually test this but it should generally be what your looking for. Also before running these try using EXPLAIN to see how bad the join performance will be. You might benefit from adding an indexes to the tables.
On a side note (and this isn't really your question) but mysql_real_escape_string is deprecated, and in general you should not use any of the built in php mysql functions as they are all known to be unsafe. Php docs recommend using PDO instead.