Check duplicates name ignore entry - php

Question

I am using following code to insert entry in my database. But i can add same entry multiple time and i wanna that whenever i submit same entry in input type then message will show "Nickname already exists "
<div>
<form>
<div>name <input type="text" name="na"/></div>
<div>marks1 <input type="text" name="m1"/></div>
<div>marks2<input type="text" name="m2"/></div>
<div>marks3 <input type="text" name="m3"/></div>
<div> <input type="submit" name="save" value="save"/></div>
</form>
</div>
And Here is my php code:-
<?php
if(!empty($_GET['save'])){
$na=$_GET['na'];
$m1=$_GET['m1'];
$m2=$_GET['m2'];
$m3=$_GET['m3'];
$query="insert into student(name,marks1,marks2,marks3) values('$na','$m1','$m2','$m3')";
mysqli_query($connect,$query);
}
?>

Answer 1

Make a unique column in database for example unique name for every student. So when you enter new record first check it that either it is present in the database or not. If its there then you can show error to user
For example you can set a unique constraint like this

Answer 2

Do a select before inserting in your base to check if the username already exists.
For your input message showing that the username already exists you can use a hidden paragraph:<p id="informationText" hidden>This paragraph should be hidden.</p>
Then once your select request has returned that the tuple already exists do an ajax query to show up this paragraph: $('#informationText').removeAttr('hidden');
That's a simple way, there is other better way to do that you can do some research about JavaScript Form Validation
FIRST EDIT
Here is a code sample:
<?php
if( isset( $_GET['save'] ) ){
$na=$_GET['na'];
$m1=$_GET['m1'];
$m2=$_GET['m2'];
$m3=$_GET['m3'];
$query = "select * from student where name = ? ";
$result = mysqli_query( $connect,$query, array( &$na ) );
$row = mysqli_fetch_row( $result );
if (count($row) > 0) {
echo "<script>$('#informationText').text = "Username already exists";$('#informationText').removeAttr('hidden');</script>";
} else {
$query="insert into student(name,marks1,marks2,marks3) values('$na','$m1','$m2','$m3')";
mysqli_query($connect,$query);
}
}
?>