Cascade

We may get FK constraint exception when we try to delete the parent record (e.g., Player table). We can define database level cascade such as "on delete cascade|set null".

  create table player_stats (
      `id` integer unsigned not null auto_increment,
      `player_id` integer unsigned not null,
      primary key (`id`),
      foreign key (`player_id`) references player (`id`) on delete cascade
  )
  engine = InnoDB;

Note that it is uni-directional. Only works for parent -> child cascade.

With Hibernate cascade, we don't need to define this on DDL. And the cascade is more flexible - bi-directional. We can cascade change from any side following the association link (one-to-many, many-to-one, many-to-many etc). It handles cascade on higher level, i.e., entity to entity. On example is tbl_apGroup, tbl_apGroup_ap, tbl_ap. The database cascade would be defined on FK tbl_apGroup_ap referencing to tbl_apGroup. But Hibernate cascade is from domain object ApGroup to Ap.