mysql> EXPLAIN SELECT COUNT(*) FROM Bookinfo;
+----+-------------+----------+------------+-------+---------------+--------+---------+------+---------+----------+-------------+
| id | select_type | table    | partitions | type  | possible_keys | key    | key_len | ref  | rows    | filtered | Extra       |
+----+-------------+----------+------------+-------+---------------+--------+---------+------+---------+----------+-------------+
|  1 | SIMPLE      | Bookinfo | NULL       | index | NULL          | ISBN13 | 41      | NULL | 1093622 |   100.00 | Using index |
+----+-------------+----------+------------+-------+---------------+--------+---------+------+---------+----------+-------------+
1 row in set, 1 warning (0.00 sec)