Fatal error: Uncaught mysqli_sql_exception: Unknown column 'staff_master.staff_id' in 'SELECT' in /var/www/html/nonteaching.php:51 Stack trace: #0 /var/www/html/nonteaching.php(51): mysqli_query(Object(mysqli), 'SELECT CONCAT('...') #1 {main} thrown in /var/www/html/nonteaching.php on line 51