How can you effectively handle errors in MySQL queries in PHP using mysql_error()?

When executing MySQL queries in PHP, errors can occur due to various reasons such as syntax errors, connection issues, or data validation problems. To effectively handle these errors, you can use the `mysql_error()` function to retrieve the error message generated by the most recently executed MySQL function. This message can then be used to display an appropriate error message to the user or log the error for debugging purposes.

// Execute MySQL query
$result = mysql_query($query);

// Check for errors
if (!$result) {
    $error_message = mysql_error();
    // Display or log the error message
    echo "Error: " . $error_message;
} else {
    // Process the query result
}