How to check if a row exists in MySQL? (i.e. check if an email exists in MySQL)
I need help checking if a row exists in the database. In my case, that row contains an email address. I am getting the result:
email no longer exists [email protected]
This is the code I'm currently using:
if (count($_POST)) {
$email = $dbl->real_escape_string(trim(strip_tags($_POST['email'])));
$query = "SELECT `email` FROM `tblUser` WHERE `email` = '$email'";
$result = mysqli_query($dbl, $query);
if (is_resource($result) && mysqli_num_rows($result) == 1) {
$row = mysqli_fetch_assoc($result);
echo $email . " email exists " . $row["email"] . "\n";
} else {
echo "email no longer exists" . $email . "\n";
}
}
Is there a better way to check if a row exists in MySQL (in my case, check if an email exists in MySQL)?
Answer
The following are tried, tested and proven methods to check if a row exists.
(Some of which I use myself, or have used in the past).
Edit: I made an previous error in my syntax where I used mysqli_query() twice. Please consult the revision(s).
I.e.:
if (!mysqli_query($con,$query)) which should have simply read as if (!$query).
- I apologize for overlooking that mistake.
Side note: Both '".$var."' and '$var' do the same thing. You can use either one, both are valid syntax.
Here are the two edited queries:
$query = mysqli_query($con, "SELECT * FROM emails WHERE email='".$email."'");
if (!$query)
{
die('Error: ' . mysqli_error($con));
}
if(mysqli_num_rows($query) > 0){
echo "email already exists";
}else{
// do something
}
and in your case:
$query = mysqli_query($dbl, "SELECT * FROM `tblUser` WHERE email='".$email."'");
if (!$query)
{
die('Error: ' . mysqli_error($dbl));
}
if(mysqli_num_rows($query) > 0){
echo "email already exists";
}else{
// do something
}
You can also use mysqli_ with a prepared statement method:
$query = "SELECT `email` FROM `tblUser` WHERE email=?";
if ($stmt = $dbl->prepare($query)){
$stmt->bind_param("s", $email);
if($stmt->execute()){
$stmt->store_result();
$email_check= "";
$stmt->bind_result($email_check);
$stmt->fetch();
if ($stmt->num_rows == 1){
echo "That Email already exists.";
exit;
}
}
}
Or a PDO method with a prepared statement:
<?php
$email = $_POST['email'];
$mysql_hostname = 'xxx';
$mysql_username = 'xxx';
$mysql_password = 'xxx';
$mysql_dbname = 'xxx';
try {
$conn= new PDO("mysql:host=$mysql_hostname;dbname=$mysql_dbname", $mysql_username, $mysql_password);
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException $e) {
exit( $e->getMessage() );
}
// assuming a named submit button
if(isset($_POST['submit']))
{
try {
$stmt = $conn->prepare('SELECT `email` FROM `tblUser` WHERE email = ?');
$stmt->bindParam(1, $_POST['email']);
$stmt->execute();
while($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
}
}
catch(PDOException $e) {
echo 'ERROR: ' . $e->getMessage();
}
if($stmt->rowCount() > 0){
echo "The record exists!";
} else {
echo "The record is non-existant.";
}
}
?>
- Prepared statements are best to be used to help protect against an SQL injection.
N.B.:
When dealing with forms and POST arrays as used/outlined above, make sure that the POST arrays contain values, that a POST method is used for the form and matching named attributes for the inputs.
- FYI: Forms default to a GET method if not explicity instructed.
Note: <input type = "text" name = "var"> - $_POST['var'] match. $_POST['Var'] no match.
- POST arrays are case-sensitive.
Consult:
Error checking references:
- http://php.net/manual/en/function.error-reporting.php
- http://php.net/manual/en/mysqli.error.php
- http://php.net/manual/en/pdo.error-handling.php
Please note that MySQL APIs do not intermix, in case you may be visiting this Q&A and you're using mysql_ to connect with (and querying with).
- You must use the same one from connecting to querying.
Consult the following about this:
If you are using the mysql_ API and have no choice to work with it, then consult the following Q&A on Stack:
The mysql_* functions are deprecated and will be removed from future PHP releases.
- It's time to step into the 21st century.
You can also add a UNIQUE constraint to (a) row(s).
References: