When you add following entity to a MySQL database:

@Entity
public class Person {
  @Id
  @GeneratedValue
  private long id;
  private String name;
}

Hibernate 4 sends following correct SQL insert statement to the database

insert into Person(name) values (?)

This insert statement does not provide a value for the field id:
this field is correctly (based on @GeneratedValue) presumed to be autonumer.

Hibernate 5 sends following SQL statement to the database

select next_val as id_val from hibernate_sequence for update

which gives an error, as the table hibernate_sequence does not exist