GBase8s如何在有外键关系的表中删除数据？有几种方式，分别是什么？
有两种方式：
1、先删除外键表中的数据，再删除当前数据
举例：
drop table if exists t1;
drop table if exists t2;
create table t1(id int primary key , s1 float);
create table t2(id int , id1 int ,s1 float,foreign key(id1) references t1(id) );
insert into t1 values(1,20);
insert into t1 values(2,30);
insert into t2 values(1,1,50);
--如果你直接删除t1的数据，则报错
delete t1;
692: Key value for constraint (root.u143_565) is still being referenced.
Error in line 1
Near character position 8
--需要先删除t2表中的数据，才能删除t1表中的数据
delete t2;
delete t1;
2、可以通过外键设置级联删除
--在设置外键时，设置级联删除
drop table t2;
drop table t1;
create table t1(id int primary key , s1 float);
create table t2(id int , id1 int ,s1 float,foreign key(id1) references t1(id) on delete cascade);
insert into t1 values(1,20);
insert into t1 values(2,30);
insert into t2 values(1,1,50);
--此时删除t1的数据，则删除t1及t2中数据
delete t1;
2 row(s) deleted.
select * from t2;
id id1 s1
No rows found.