sqlite3的外键约束不好使？
drop table t_group;
drop table t_user;
create table t_group
(
id integer,
primary key (id)
);
create table t_user
(
id integer,
name text,
groupId integer,
primary key(id),
foreign key (groupId) references t_group(id) on delete cascade on update cascade
);
insert into t_group values(1);
insert into t_group values(2);
insert into t_user values(1,"j",2);
insert into t_user values(2,"a",3);
