Auto Increment after delete in MySQL

Question

I have a MySQL table with a primary key field that has AUTO_INCREMENT on. After reading other posts on here I\'ve noticed people with the same problem and with varied answer

Answer 1

if($id == 1){ // deleting first row
            mysqli_query($db,"UPDATE employees  SET id=id-1 WHERE id>1");
        }
        else if($id>1 && $id<$num){ // deleting middle row
            mysqli_query($db,"UPDATE employees  SET id=id-1 WHERE id>$id");
        }
        else if($id == $num){ // deleting last row
            mysqli_query($db,"ALTER TABLE employees AUTO_INCREMENT = $num");
        }
        else{
            echo "ERROR";
        }

        mysqli_query($db,"ALTER TABLE employees AUTO_INCREMENT = $num");