How to check if a row exists in MySQL? (i.e. check if an email exists in MySQL)

Question

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 database (in my case, check if an email exists in MySQL)?

Answer 1

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.

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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:

• http://php.net/manual/en/tutorial.forms.php

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:

• Can I mix MySQL APIs in PHP?

If you are using the mysql_ API and have no choice to work with it, then consult the following Q&A on Stack:

• MySql php: check if Row exists

The mysql_* functions are deprecated and will be removed from future PHP releases.

• It's time to step into the 21st century.

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You can also add a UNIQUE constraint to (a) row(s).

References:

• http://dev.mysql.com/doc/refman/5.7/en/constraint-primary-key.html
• http://dev.mysql.com/doc/refman/5.7/en/alter-table.html
• How to check if a value already exists to avoid duplicates?
• How add unique key to existing table (with non uniques rows)