How can you prevent duplicate line numbers from being inserted into a database when updating entries in PHP?

To prevent duplicate line numbers from being inserted into a database when updating entries in PHP, you can first check if the line number already exists in the database before inserting it. If it does exist, you can update the existing entry instead of inserting a new one. 

// Check if line number already exists in the database before updating
$line_number = $_POST['line_number'];
$query = "SELECT * FROM your_table WHERE line_number = $line_number";
$result = mysqli_query($connection, $query);

if(mysqli_num_rows($result) > 0) {
    // Update existing entry
    $update_query = "UPDATE your_table SET column1 = 'value1', column2 = 'value2' WHERE line_number = $line_number";
    mysqli_query($connection, $update_query);
} else {
    // Insert new entry
    $insert_query = "INSERT INTO your_table (line_number, column1, column2) VALUES ('$line_number', 'value1', 'value2')";
    mysqli_query($connection, $insert_query);
}

Keywords

PHP database duplicate line numbers prevention

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