create table t1
(id int not null primary key,
 de varchar(5)
)

insert into t1
select 1,'a' union all
select 2,'b' union all
select 3,'c'

create table t2
(id int not null
 constraint fk_t1_id foreign key references t1(id) 
 on delete cascade
)

insert into t2(id) values(1)
insert into t2(id) values(3)

-- 删除t1.id=1,级联删除t2.id=1.
delete from t1 where id=1

select * from t1
/*
id          de
----------- -----
2           b
3           c
*/

select * from t2
/*
id
-----------
3
*/