I created a function to add and return the average rating.Rating Function// Adding AddRating     final function AddRating($rt_target_id, $u_id, $rt_vote,$moduleName){        $error  = 0;        if(!empty($moduleName) && $rt_target_id != 0 && $u_id != 0){            $tableName =  '';            switch ($moduleName) {                case 'promotion':                $tableName = 'ws_promotion';                break;                default:                $tableName = 'invalid';            }            if($tableName!='invalid'){                $addRating = INSERT INTO ws_rating (u_id, rt_target_id, rt_vote, rt_table_name, date_added)                 VALUES ('.$u_id.','.$rt_target_id.','.$rt_vote.','.$tableName.', '.date(Y-m-d H:i:s).');                $dataInsert = mysqli_query($this->connection,$addRating);                if($dataInsert){                    $Rating = select avg(rt_vote) as Rating from `ws_rating` where `rt_target_id` = .$rt_target_id.  and `rt_table_name` = '.$tableName.';                    $RatingQuery = mysqli_query($this->connection,$Rating);                    $rowRating = mysqli_fetch_assoc($RatingQuery);                    $response['rating'] =  $rowRating;                  }                echo json_encode($response);            }        }// end if    }Table---------------------------------------------------------------------|rt_id | u_id | rt_target_id | rt_vote | rt_table_name | date_added |-------------------------------------------------------------------|1     | 1    | 2            | 5       | promotion_tb | 2016-03-24  |---------------------------------------------------------------------I added 12432 rows with same data in above table. Below select query is giving this 4.9936 result of added rows 12432. SELECT AVG(rt_vote) AS Rating FROM `ws_rating` WHERE `rt_target_id` = 2 AND `rt_table_name` = 'ws_promotion'I wanted to know whether my table structure and function are correct.  In the future, if there are 1 million rows then will my function return the correct average?
PHP rating function for getting the average value of column
php;mysqli;statistics