MySQL 8.0

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create table parents (
    id int not null,
    primary key (id)
);

create table children (
    id int, 
    parent_id int,
    foreign key (parent_id) 
        references parents(id)
        on delete cascade
);
insert into parents values (1), (2);
insert into children values (1, 1), (2, 1), (3, 2);

delete from parents where id = 1;

select * from children;


id
parent_id


3
2