mysql> show create table t;
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                                         |
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| t     | CREATE TABLE `t` (
  `i` varchar(20) NOT NULL,
  PRIMARY KEY (`i`) /*T![clustered_index] NONCLUSTERED */
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin |
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> insert into t values ('a');
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1  Changed: 0  Warnings: 0

mysql> begin;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from t;
+---+
| i |
+---+
| a |
+---+
1 row in set (0.00 sec)

mysql> update t set i = 'a'; -- insert into t values ('a') in another session
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1  Changed: 0  Warnings: 0

mysql> update t set i = 'b'; -- insert into t values ('b') in another session
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> rollback;
Query OK, 0 rows affected (0.00 sec)