verify input from database

[erin_grey]

i have a mysql database with a table containing device numbers.
the text field allows the user to input a device number.

my problem:
1. how to validate user input by checking the database.
2. if the input is invalid, how will i display an error message?

[barand]

I f there are not too many (subjective judgement required here) you could create a list box or dropdown so they can only select a correct one in the first place.

Otherwise

select devicenum from table where devicenum = $_POST['devicenum']"

and check the number or recs returned > 0 to see if exists.

Output error messge when you redisplay the form