PostgreSQL - 正确更改表行的ID

Question

如何更改某些表行的id？

喜欢:

UPDATE table SET id=10 WHERE id=5;

但是,它会将更改级联到每个引用此表的其他表的更改？

我想这样做,因为我需要从另一个具有大多数相同表的数据库导入数据,但是ID不同.因此,如果id与旧数据库匹配,则更容易正确导入数据.

Answer 1

假设你有这两个表:

create table referenced (id integer primary key);
create table referencer (a integer references referenced (id));

引用的表引用器引用表:

=> \d referencer
  Table "public.referencer"
 Column |  Type   | Modifiers 
--------+---------+-----------
 a      | integer | 
Foreign-key constraints:
    "referencer_a_fkey" FOREIGN KEY (a) REFERENCES referenced(id)

然后在两者中插入一个值:

insert into referenced values (1);
insert into referencer values (1);

select *
from
    referenced rd
    inner join
    referencer rr on rd.id = rr.a
;
 id | a 
----+---
  1 | 1

现在您要将引用更改为on update cascade:

alter table referencer
    drop constraint referencer_a_fkey,
    add foreign key (a) references referenced (id) on update cascade;

并更新它:

update referenced set id = 2;

select *
from
    referenced rd
    inner join
    referencer rr on rd.id = rr.a
;
 id | a 
----+---
  2 | 2

现在,如果已更新的ID已存在,则在引用的表主键中将出现另一个问题.但那会产生另一个问题.

UPDATE

这很危险,所以首先备份数据库.必须以超级用户身份完成:

update pg_constraint
set confupdtype = 'c'
where conname in (
    select
        c.conname
    from
        pg_constraint c
        inner join
        pg_class referenced on referenced.oid = c.confrelid
    where
        referenced.relname = 'referenced'
        and
        c.contype = 'f'
);

它会将引用表上的所有外键约束更改为 on update cascade

Answer 2

您将需要更改外键并将ON UPDATE操作设置为CASCADE。当您更改值时，所有关联的值也会更改。

这是如何定义它的示例：

CREATE TABLE order_items (
    product_no integer REFERENCES products ON UPDATE CASCADE,
    order_id integer REFERENCES orders ON UPDATE CASCADE,
    quantity integer,
    PRIMARY KEY (product_no, order_id)
);

有关更多信息，请参阅http://www.postgresql.org/docs/current/static/ddl-constraints.html