Delete query removes same records in any row - php

Question

In my code, sql query deletes the record in table with same name. For example, I have 2 records with same name mani & mani. This code deletes 2 records.
form Code:
<form method="post" action="admin.php">
<h3>Delete a user</h3>
<select name="username">
<?php
$sql = mysqli_query($connection, "SELECT username FROM users");
while ($row = $sql->fetch_assoc()){?>
<option value="<?php echo $row['username']; ?>"><?php echo
$row['username']; ?></option>
<?php }?>
</select>
<input type="submit" name="delete" value="Delete User">
</form>
Sql
<?php
include('connect.php');
if(isset($_POST['delete'])) {
$username = $_POST['username'];
mysqli_query($connection, "DELETE FROM `users` WHERE `username` = '$username' ");
echo "User was deleted!";
}
?>

Answer 1

You need to select unique value such as ID in this case
Try this one:
<form method="post" action="admin.php">
<h3>Delete a user</h3>
<select name="username">
<?php
$sql = mysqli_query($connection, "SELECT username FROM users");
while ($row = $sql->fetch_assoc()){?>
<option value="<?php echo $row['user_id']; ?>"><?php echo
$row['username']; ?></option>
<?php }?>
</select>
<input type="submit" name="delete" value="Delete User">
</form>
SQL
<?php
include('connect.php');
if(isset($_POST['delete'])) {
$user_id = $_POST['user_id'];
mysqli_query($connection, "DELETE FROM `users` WHERE user_id = '$user_id' ");
echo "User was deleted!";
}
?>

Answer 2

Yes, your code will delete rows with matching names because you have Query :
DELETE FROM `users` WHERE `username` = '$username'
To delete specific row you need to use some unique value to refer the row, like primary key!
Say for example :
If a user has EmployeeId, CustomerId or StudentRollNo; you could use these options in where clause. These tips are very basic things in Query.