How can empty or NULL values in a database query affect data consistency and integrity in PHP applications?

Empty or NULL values in a database query can affect data consistency and integrity in PHP applications by potentially causing unexpected behavior or errors when processing the results. To address this issue, it is important to handle NULL values properly in the query and in the PHP code to ensure that the data is handled correctly.

// Example of handling NULL values in a database query in PHP
$query = "SELECT * FROM table WHERE column IS NOT NULL";
$result = mysqli_query($connection, $query);

if ($result) {
    while ($row = mysqli_fetch_assoc($result)) {
        // Handle the data from the query result
    }
} else {
    // Handle the query error
}