创建和删除外键

创建外键

postgres=# create table t_p(f1 int not null,f2 int ,primary key(f1));
create table t_f(f1 int not null,f2 int );NOTICE:  Replica identity is needed for shard table, please add to this table through "alter table" command.
CREATE TABLE
postgres=# create table t_f(f1 int not null,f2 int );
NOTICE:  Replica identity is needed for shard table, please add to this table through "alter table" command.
CREATE TABLE
postgres=# ALTER TABLE t_f ADD CONSTRAINT t_f_f1_fkey FOREIGN KEY (f1) REFERENCES t_p (f1);
ALTER TABLE
postgres=# 

外键只是同一个节点内约束有效果，所以外键字段和对应主键字段必需都是表的分布键，否则由于数据分布于不同的节点内会导致更新失败。

删除外键

postgres=# ALTER TABLE t_f DROP  CONSTRAINT t_f_f1_fkey;  
ALTER TABLE
postgres=#