问如何选择一个记录，更新它，并确保它的平均值没有被更新？

EN

//last id being the id of the last query set or updated
$last_id = $mysql->insert_id;

if($last_id != $id) {
//execute code
{
else {

echo "last id already in database!";

}

//define input variables
$lesson_id = $_POST['lesson_id'];
$user_id = $_POST['user_id'];
$instructor_id = $_POST['instructor_id'];
$lesson_comments = $_POST['lesson_comments'];
$lesson_date = date("Y-m-d");
$video_ids = isset($_POST['checkbox']) ? $_POST['checkbox'] : array();  # this is  called a ternary operator

//insert lesson information first
$query ="INSERT INTO swing_viewer_lessons (lesson_id, user_id, instructor_id,      lesson_comments, lesson_date) VALUES (?, ?, ?, ?, ?)";
if ($stmt = $mysqli->prepare($query)) {
$stmt->bind_param("iiiss", $lesson_id, $user_id, $instructor_id, $lesson_comments,    $lesson_date);
$stmt->execute();
//printf($stmt->error);
echo "successful";
//echo "$last_id";
}

//insert lesson information
if (is_array($video_ids) && count($video_ids) > 0)
{
foreach($video_ids as $list);   
}   

// Make it into a comma separated list
$rec_ids = implode(',', $video_ids);    

//get last inserted id from above
$last_id= $mysqli->insert_id;

//finally query and update lesson information based on the last id added from above
$query ="UPDATE swing_viewer_lessons SET video_ids=? WHERE id=?";
if ($stmt = $mysqli->prepare($query)) {
$stmt->bind_param("si", $rec_ids, $last_id);
$stmt->execute();
}