Question

I want have an insert query, but before inserting I check whether the username and email are used by someone else. If used, I want to cancel insert query and echo a message to say whether username or email is in use.

Here my code:

$sql = "SELECT 1 FROM user WHERE username='".$_POST['username']."'";
if(!$result = mysql_query($sql))
    die(mysql_error());
while($row = mysql_fetch_array($result))
    die('This username is already exists');
$sql = "SELECT 2 FROM user WHERE email='".$_POST['email']."'";
if(!$result = mysql_query($sql))
    die(mysql_error());
while($row = mysql_fetch_array($result))
    die('This email address is already exists');
$sql = "insert into user (username,email,password,tel,type) values ('".$_POST['username']."','".$_POST['email']."','".$_POST['password']."','".$_POST['telnumber']."','member')";
if(!mysql_query($sql))
    die(mysql_error());

I want these three sql statements in one. It can be either using cases or something else that you suggest. So,
Is it possible to zip this code into one sql query?

As a result what I need is

sql = "sql_query"
if(!$result = mysql_query($sql))
    die(mysql_error());
while($row = mysql_fetch_array($result)){
if($row['result']==1)
    die('This username is already exists');
else if($row['result']==2)
    die('This email is already exists');
}
die('you have succesfully registered');

thanks for any advice.

Answer 1

While I suggest you follow @cularis’ answer, you may be interested in the following alternative:

1. Give email and username the UNIQUE constraint, by creating a unique index for both of these.
2. run your INSERT query, and if this fails… (due to duplicate keys)
3. run the suggested combined SELECT, to determine which field existed (username or email)