postgresql外键on delete cascade

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级联删除

A表中字段依赖于B表中对应字段，
如果删除B表中的记录，则会级联删除A表中对应记录

create table test(id serial primary key, name varchar(10));

create table test01(id serial primary key, tid int, constraint fk_test01_tid foreign key(tid) references test(id) 
on delete cascade);

imos=# insert into test(name) values('a'),('b'),('c');
INSERT 0 3
imos=# insert into test01(tid) values(1),(2),(3);
INSERT 0 3
imos=# 
imos=# select * from test;
 id | name 
----+------
  1 | a
  2 | b
  3 | c
(3 rows)

imos=# select * from test01;
 id | tid 
----+-----
  1 |   1
  2 |   2
  3 |   3

imos=# delete from test where id=1;
DELETE 1
imos=# select * from test01;
 id | tid 
----+-----
  2 |   2
  3 |   3
(2 rows)

imos=# select * from test;
 id | name 
----+------
  2 | b
  3 | c
(2 rows)

imos=# delete from test01 where id=2;
DELETE 1
imos=# select * from test;
 id | name 
----+------
  2 | b
  3 | c
(2 rows)

imos=# select * from test01;
 id | tid 
----+-----
  3 |   3
(1 row)