MySQL query question

[Designer]

Hi guys,

I'm trying to determine if a row or multiple rows in a database exist with specific data in them.

What i've got is a DB with 4 fields, one of which is username, i want to check to see if the username exists already in the database to prevent the name being added multiple times, (im doing this in PHP) so the script should add the row's if the username isnt in the DB already or should amend them if they already exist.

Here's my code so far, could you look over it and see what im doing wrong

PHP Code:

$query=" SELECT * FROM quartertime WHERE user='$user'";   //Query the DB to check if user exists
$result=mysql_query($query);
$num=mysql_numrows($result);
if ($num !="0")
{                                    //if record exists

$query = "UPDATE quartertime SET user = '$user', car = '$car', qmtime = '$quartertime' WHERE user = '$user'";
mysql_query($query);
$imdoing="Updating existing record";

} else {    
                                                    //if record doesnt exist
$query = "INSERT INTO quartertime ( user, car, qmtime );   
values ( '$user', '$car', '$quartertime')";
@mysql_query( $query);
$imdoing="Adding new record";                                            
} 


When that page loads it seems to always try and amend non-existant records, i wasnt overly sure what i should be looking for in the first query to determine if the record(s) exist or not. the field i want to examine is 'user' and compare it to the variable $user.

Thanks

[Deitel]

I don't know how to use php but i think you may have a mistake in you sql code.

When you are comparing with a string, u must make sure that the string is in " ' ", i.e.

select * from users where users_name='deitel';

so by the look of your code, the sql is searching for a user called $user. Now as I said, I dont know how to use php, but in delphi i add to the string, i.e.

sql := "select * from users where users_name='" + usernamevariable + "';";

if you catch my drift. That may be your problem

[Designer]

I've just found the mistake
changed this

PHP Code:

mysql_query($query); 


to this

PHP Code:

@mysql_query($query); 


and missed a ; later on

By the way the $user is a variable, it's value is obtained higher up the script and is imported from the forum database

Anyways, ran into one other PHP problem and that's how do I validate the user's input for the $quartertime variable, this is taken from a text entry field on a different page.
I am expecting to see values greater than 3 but not greater than 30, it can also be values to 3 decimal places i.e 10.345 would be ok but not to 4 decimal places, i want to reject anything outside of these conditions (mainly to prevent people typing into the box and submitting it )

Thanks