PostgreSQL继承和外键引用父表 [英] Postgresql inheritance and foreign key referencing parent table

问题描述

我已经对此进行了文档记录，并阅读了其他用户对此的文章，但是在我的情况下，引用应该可以正常工作：我有几个表扩展了一个实体表和一个关联表，仅引用了实体表。因此，我仅引用拥有其他所有表ID的父表。

I already documented about this and read other users post about this on so, but in my case the referencing should be working fine: I have several tables extending one "entity" table and an "association" table referencing just "entity" table. So I'm referencing just the parent table which own every other table id. How come I get the following then?

ERROR:  insert or update on table "association" violates foreign key constraint "association_id1_fkey"
DETAIL:  Key (id1)=(1) is not present in table "entity".

这里是我正在使用的架构。

Here is the schema I'm using.

CREATE TABLE entity (
    id serial primary key,
    created_at int,
    updated_at int,
    deleted_at int
);

CREATE TABLE association (
    id1 int references entity(id) on delete cascade on update cascade,
    atype varchar,
    id2 int references entity(id) on delete cascade on update cascade,
    created_at int,
    deleted_at int
);

CREATE TABLE "user" (
    first_name varchar(255),
    last_name varchar(255)
)INHERITS(entity);

CREATE TABLE "pet" (
    name varchar(255)
)INHERITS(entity);

INSERT INTO "user" (first_name) VALUES ('damiano');
INSERT INTO "user" (first_name) VALUES ('francesco');
INSERT INTO "user" (first_name) VALUES ('romolo');

INSERT INTO "pet" (name) VALUES ('baloo');
INSERT INTO "pet" (name) VALUES ('micia');
INSERT INTO "pet" (name) VALUES ('ioria');

INSERT INTO "association" VALUES (1, 'pets', 4, 0, 0);
INSERT INTO "association" VALUES (1, 'pets', 5, 0, 0);
INSERT INTO "association" VALUES (2, 'pets', 4, 0, 0);
INSERT INTO "association" VALUES (2, 'pets', 5, 0, 0);
INSERT INTO "association" VALUES (3, 'pets', 6, 0, 0);

正确插入行：

testing=# select * from "entity";
 id | created_at | updated_at | deleted_at 
----+------------+------------+------------
  1 |            |            |           
  2 |            |            |           
  3 |            |            |           
  4 |            |            |           
  5 |            |            |           
  6 |            |            |           
(6 rows)

testing=# select * from "user";
 id | created_at | updated_at | deleted_at | first_name | last_name 
----+------------+------------+------------+------------+-----------
  1 |            |            |            | damiano    | 
  2 |            |            |            | francesco  | 
  3 |            |            |            | romolo     | 
(3 rows)

testing=# select * from "pet";
 id | created_at | updated_at | deleted_at | name  
----+------------+------------+------------+-------
  4 |            |            |            | baloo
  5 |            |            |            | micia
  6 |            |            |            | ioria
(3 rows)

testing=# 

推荐答案

父表不包含继承表中的所有数据。从该表中进行选择实际上会对继承的表执行 UNION 。

The parent table doesn't contain all the data from the inherited tables. Selecting from that table in effect does a UNION over the inherited tables.

比较以下内容：

SELECT * FROM "entity";
SELECT * FROM ONLY "entity";

这就是为什么不再使用继承的原因。

That's why inheritance isn't used more.

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