How can I check if a value already exists in mySQL database? - php

Question

I want to store a name in the mySQL database. When I click the submit button, PHP should check if the name already exists in the database. If yes then do not submit and print an error message:
Name already exists in database.
<?php
if ( !empty($_POST)) {
$name = $_POST['name'];
$valid = true;
if ($valid) {
$pdo = Database::connect();
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$sql = "INSERT INTO people (name) values(?) ";
$q = $pdo->prepare($sql);
$q->execute(array($name));
}
}
?>
<form action="form.php" method="post">
<input name="name" type="text" value="<?php echo !empty($name)?$name:'';?>">
<button type="submit" >Submit</button>
</form>

Answer 1

Try following query to check if a value already exists in mySQL database?
$q = $pdo->prepare("SELECT name FROM people WHERE name = :name LIMIT 1");
$q->bindValue(':name', '$name');
$q->execute();
if ($q->rowCount() > 0){
$check = $q->fetch(PDO::FETCH_ASSOC);
$row = $check['name'];
// Do Something If name Already Exist
} else {
// Do Something If name Doesn't Exist
}

Answer 2

you could declare the column as unique and check if the query executes or not, for example:
$query = $pdo->prepare("SELECT name FROM table WHERE name = :name");
$query->bindValue(':name', '$name');
if ($query->execute()){
//no duplicate
}
else {
//error, check the error code.
echo "$stmt->errorCode()";
}
$query-> execute will retun true on success and false other wise, and the database will return an error when the input is a duplicate in a unique coulmn.
I think Making the duplication check in the database is safer.