Store your zipcodes as CHAR(5) instead of a numeric type, or have your application pad it with zeroes when you load it from the DB. A way to do it with PHP using sprintf()
:
echo sprintf("%05d", 205); // prints 00205
echo sprintf("%05d", 1492); // prints 01492
Or you could have MySQL pad it for you with LPAD()
:
SELECT LPAD(zip, 5, '0') as zipcode FROM table;
Here’s a way to update and pad all rows:
ALTER TABLE `table` CHANGE `zip` `zip` CHAR(5); #changes type
UPDATE table SET `zip`=LPAD(`zip`, 5, '0'); #pads everything