Relationship between tables-foreign key

set up:

• Create a new table: create table table name (A int, B text, constraint rule name foreign key (field name) references table name (field name));
• In the establishment of the built table: alter table table name add constraint rule name foreign key (field name) references table name (field name));
• other:
  on update cascade cascade update
  on delete cascade cascade delete
  set foreign_key_checks=0 disable primary key
  set foreign_key_checks=1 enable foreign key
  alter table table name drop foreign key constraint name delete foreign key

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