check new username

rborc415

HI: you've all been soo helpful with other php issues i've had, and I thank you for it.
Here's another: How do I put a check new user server behavior into an update record behavior?

I have a form displaying a member's data (already in the database), underneath is a form to create user name and password. How do I check if the username already exists??

Thanks
rborc415

laserlight

rborc415 wrote:
How do I check if the username already exists??

Simply select a count of the users with the given username.

Of course, if you want to absolutely avoid a race condition where two users choose the same username at around the same time then you have to declare the username column as UNIQUE and then check for a unique constraint violation.

djjjozsi

here is a function, to check if the selected entry is in the database:

<?
//here comes the connection to the database:

function check_data($content,$table,$field)
{
$sql="SELECT * FROM $table WHERE $field='".mysql_real_escape_string($content)."'";
if (mysql_num_rows(mysql_query($sql))>0)
return(true);
else
return(false);
}

if(check_data($_POST["username_from_the_form"], "users_table", "username_field")==true)
print "This username is already in the table...";
else
{
print "This username isn't in the table...";
//lets do something in that case...
}


?>

laserlight

However, djjjozsi's function selects too much: you do not need to select everything if all you want is a count (or in fact, merely a check for existence, so perhaps some kind of EXISTS query would be even better).