okay, slowly:
a) if you don't want to change your data, you don't need DATE_FORMAT.
b) but you will always have trouble using this date string in comparisons.
if you want to leave it at this, I'm afraid I can't help you a lot.
if you consider changing it, I can give you a hand, it's not that difficult altogether, even if you already have data of a different type and code that uses it. I'll post it for anyone else who may come across this thread.
STEP 1: convert the old MM/DD/YYYY data
instead of the steps outlined above, you can as well do it in one statement (I had to test this first)
UPDATE table_name SET date_column = CONCAT(SUBSTRING(date_column, 7, 4), SUBSTRING(date_column, 1, 2), SUBSTRING(date_column, 4, 2))
(if your old format is different from MM/DD/YYYY, change the numbers passed to SUBSTR if necessary - first one is start position, second is length.)
STEP 2: change the column type
ALTER TABLE table_name CHANGE date_column date_column DATE
STEP 3: check your code for INSERT and UPDATE statements
You need to modify these to follow the new format, so if you e.g. had '$month/$day/$year' before, it would be '$year-$month-$day' or $year$month$day now (either works)
STEP 4: check your code for SELECT statements
To retrieve the date in the previous formatting, use DATE_FORMAT in your select statement:
SELECT DATE_FORMAT(date_column, '%m/%d/%Y') AS fdate, other_column_names FROM table_name
