Today I started to port a MySql database to PostgreSQL and I have a problem with the foreign keys and their 'sharing'
I don't know how to explain that so here is some pseudo code of the create script:
create table id_generator (
id serial PRIMARY KEY,
description varchar(50) );
create table parent (
id REFERENCES id_generator(id),
--content );
create table child (
id REFERENCES id_generator(id),
id_parent REFERENCES parent(id),
--content );
So I use one table as 'id_generator' to create the id's and to give the other tables a reference to a value table. In MySql I had no problems with that so I want that to work in PostgreSQL as well.
When running that script I get the error, that I need a primary key / unique on the table parent to create a reference on it. so I changed it into:
create table id_generator (
id serial PRIMARY KEY,
description varchar(50) );
create table parent (
id REFERENCES id_generator(id) PRIMARY KEY,
--content );
create table child (
id REFERENCES id_generator(id),
id_parent REFERENCES parent(id),
--content );
so the server accepts the create script and all is set up for some inserts.
I create the first id with:
insert into id_generator(description) values("parentID");
then I want to add a parent:
insert into parent(id, /*content*/) values(1, /*content*/);
that also works as expected, so I need to insert a child for parent:
insert into id_generator(description) values("childID");
insert into child(id,id_parent)values(2,1);
and here I get the error message "ERROR: duplicate key value violates unique constraint DETAIL: key (id_parent)=(1) allready exists"
edit:
\d child;
Tabelle ╗public.child½
Spalte | Typ | Attribute
-------------------+---------+-----------
id | integer | not null
id_parent | integer |
Indexe:
"child_pkey" PRIMARY KEY, btree (id)Fremdschlⁿssel-Constraints:
"child_id_parent_fkey" FOREIGN KEY (id_parent) REFERENCES parent(id)
"child_id_generator_fkey" FOREIGN KEY (id) REFERENCES id_generator(id)
how can I solve that?
Ok, I am sorry, problem solved, had a double call of the insert statement :facepalm:
Related
I can not add a referential constraint, both tables has the two columns id and version as primary key. I will only check the integrity that the row is existing without checking version.
CREATE TABLE TABLEE
(ID INTEGER NOT NULL,
VERSION INTEGER NOT NULL,
PRIMARY KEY (ID , VERSION);
CREATE TABLE CHAIR
(ID INTEGER NOT NULL,
VERSION INTEGER NOT NULL,
ID_TABLEE INTEGER,
PRIMARY KEY (ID , VERSION);
ALTER Chair
ADD constraint MYC FOREIGN KEY (ID)
REFERENCES TABLEE (ID)
ON DELETE RESTRICT
Got this error
[Code: -573, SQL State: 42890] A column list specified in the references clause of constraint "MYC " does not identify a unique constraint of the parent table or nickname "TABLEE".. SQLCODE=-573, SQLSTATE=42890, DRIVER=4.28.11
The problem here is that Tablee its primary key consists of two columns id and version. But the integrity check should only be made on the referenced id, not version.
To establish a foreign key on a table the referenced column needs to:
Be a primary key on the other table.
...or at least act as one.
Since you already have a primary key on the referenced table, you can use the second approach and add a UNIQUE and NOT NULL constraints on ID.
For example:
CREATE TABLE TABLEE (
ID INTEGER NOT NULL,
VERSION INTEGER NOT NULL,
PRIMARY KEY (ID , VERSION),
constraint uq1 unique (id) -- added UNIQUE constraint on ID
);
CREATE TABLE CHAIR (
ID INTEGER NOT NULL,
VERSION INTEGER NOT NULL,
ID_TABLEE INTEGER,
PRIMARY KEY (ID , VERSION)
);
ALTER table Chair
ADD constraint MYC FOREIGN KEY (ID)
REFERENCES TABLEE (ID)
ON DELETE RESTRICT;
See running example at db<>fiddle.
Note: If you want ID to have repeated values over the table, then ID is not a key, and cannot be referenced as one.
Here is my schema for database tables:
CREATE TABLE users (
user_id INTEGER NOT NULL,
device_id INTEGER,
user_points INTEGER,
cookie VARCHAR,
PRIMARY KEY (user_id)
);
CREATE TABLE admins (
admin_id INTEGER NOT NULL,
username VARCHAR,
password VARCHAR
);
CREATE TABLE admin_adventure (
adventure_id INTEGER NOT NULL,
admin_id INTEGER,
PRIMARY KEY (adventure_id)
);
CREATE TABLE adventures (
adventure_id INTEGER NOT NULL,
prize_id INTEGER,
novella_id INTEGER,
PRIMARY KEY (adventure_id)
);
Here I'm trying to define FOREIGN KEYS:
ALTER TABLE admin_adventure ADD FOREIGN KEY ( admin_id ) REFERENCES admins ( admin_id );
ALTER TABLE admin_adventure ADD FOREIGN KEY ( adventure_id ) REFERENCES adventures ( adventure_id );
And here is the error I get when trying to migrate with Flyway:
ERROR: there is no unique constraint matching given keys for
referenced table "admins"
Can someone explain what I'm doing wrong and why I get this error?
The error message is complaining that you are trying to link a foreign key to a column in another table which is not unique (e.g. a primary key). Try making the admin_id column in the admins table a primary key:
CREATE TABLE admins (
admin_id INTEGER NOT NULL,
username VARCHAR,
password VARCHAR,
PRIMARY KEY (admin_id)
);
Like the documentation says:
A foreign key must reference columns that either are a primary key or form a unique constraint.
So you must either
ALTER TABLE admins ADD PRIMARY KEY (admin_id);
or
ALTER TABLE admins ADD UNIQUE (admin_id);
I need to add a foreign keys for two tables each other. Can this be done ?
As an example:
CREATE SCHEMA IF NOT EXISTS schema1;
CREATE TABLE schema1.tableA
(
id serial NOT NULL,
tableB_id integer,
PRIMARY KEY (id),
FOREIGN KEY (tableB_id) REFERENCES schema1.tableB (id)
);
CREATE TABLE schema1.tableB
(
id serial NOT NULL,
tableA_id integer,
PRIMARY KEY (id),
FOREIGN KEY (tableA_id) REFERENCES schema1.tableA(id)
);
Above query causes an error !
ERROR: relation "schema1.tableb" does not exist SQL state: 42P01
Can this be done or is there any better solution?
I'am using PostgreSQL version 10.5 and pgAdmin 3.6
Add the foreign keys after creating both tables:
CREATE SCHEMA IF NOT EXISTS schema1;
CREATE TABLE schema1.tableA
(
id serial NOT NULL,
tableB_id integer,
PRIMARY KEY (id)
);
CREATE TABLE schema1.tableB
(
id serial NOT NULL,
tableA_id integer,
PRIMARY KEY (id)
);
ALTER TABLE schema1.tablea
add FOREIGN KEY (tableB_id) REFERENCES schema1.tableB (id);
ALTER TABLE schema1.tableb
add foreign key (tableA_id) REFERENCES schema1.tableA(id);
i´ve got a problem with foreign keys, it´s an strange problem.
First table:
CREATE TABLE adjunto
(
id serial NOT NULL,
codigo text,
descripcion text,
usuario integer,
file integer,
nombre text,
propiedades hstore,
CONSTRAINT adjunto_pkey PRIMARY KEY (id ),
CONSTRAINT adjunto_file_fkey FOREIGN KEY (file)
REFERENCES file (file_id) MATCH SIMPLE
ON UPDATE NO ACTION ON DELETE CASCADE
) WITH (
OIDS=FALSE
);
Second table:
CREATE TABLE adjunto_coleccion_privada
(
id serial NOT NULL,
adjunto integer,
coleccion integer,
CONSTRAINT adjunto_coleccion_privada_pkey PRIMARY KEY (id ),
CONSTRAINT adjunto_coleccion_privada_adjunto_fkey FOREIGN KEY (adjunto)
REFERENCES adjunto (id) MATCH SIMPLE
ON UPDATE NO ACTION ON DELETE CASCADE,
CONSTRAINT adjunto_coleccion_privada_coleccion_fkey FOREIGN KEY (coleccion)
REFERENCES coleccion (id) MATCH SIMPLE
ON UPDATE NO ACTION ON DELETE CASCADE
)
WITH (
OIDS=FALSE
);
Command:
INSERT INTO adjunto_coleccion_privada (adjunto, coleccion)
VALUES (600, 2) RETURNING id
Values 600 and 2 exist in both tables, adjunto and colecion.
Detailed error:
Mensaje: ERROR: insert or update on table "adjunto_coleccion_privada"
violates foreign key
constraint "adjunto_coleccion_privada_adjunto_fkey"
Detail: Key (adjunto)=(600) is not present in table "adjunto".
I tested your code (I dropped the adjunto_coleccion_privada_coleccion_fkey constraint since referred table does not exist in your pasted code).
I see no problem at all.
Are you really sure that there is a record with id = 600 in the adjunto table?
I am struggling with foreign keys in my DB, possibly it has something to do with inheritance?
So here's the basic setup:
-- table address
CREATE TABLE address
(
pk_address serial NOT NULL,
fk_gadmid_0 integer NOT NULL, -- this table already exists, no problem here
street character varying(100),
zip character varying(10),
city character varying(50),
public boolean,
CONSTRAINT address_primarykey PRIMARY KEY (pk_address),
CONSTRAINT gadmid_0_primarykey FOREIGN KEY (fk_gadmid_0)
REFERENCES adm0 (gadmid_0) MATCH SIMPLE
ON UPDATE CASCADE ON DELETE NO ACTION
)
WITH (
OIDS=FALSE
);
ALTER TABLE address OWNER TO postgres;
-- table stakeholder (parent)
CREATE TABLE stakeholder
(
pk_stakeholder integer DEFAULT nextval('common_stakeholder_seq') NOT NULL,
fk_stakeholder_type integer NOT NULL, -- this table also exists, no problem here
name character varying(255) NOT NULL,
CONSTRAINT stakeholder_primarykey PRIMARY KEY (pk_stakeholder),
CONSTRAINT stakeholder_fk_stakeholder_type FOREIGN KEY (fk_stakeholder_type)
REFERENCES stakeholder_type (pk_stakeholder_type) MATCH SIMPLE
ON UPDATE CASCADE ON DELETE NO ACTION
)
WITH (
OIDS=FALSE
);
ALTER TABLE stakeholder OWNER TO postgres;
-- table individual (child of stakeholder)
CREATE TABLE individual
(
firstname character varying(50),
fk_title integer, -- this table also exists, no problem here
email1 character varying (100),
email2 character varying (100),
phone1 character varying (50),
phone2 character varying (50),
CONSTRAINT individual_primarykey PRIMARY KEY (pk_stakeholder),
CONSTRAINT title_foreignkey FOREIGN KEY (fk_title)
REFERENCES title (pk_title) MATCH SIMPLE
ON UPDATE CASCADE ON DELETE CASCADE
) INHERITS (stakeholder)
WITH (
OIDS=FALSE
);
ALTER TABLE individual OWNER TO postgres;
-- link between stakeholder and address
CREATE TABLE l_stakeholder_address
(
pk_l_stakeholder_address serial NOT NULL,
fk_stakeholder integer NOT NULL REFERENCES stakeholder,
fk_address integer NOT NULL REFERENCES address,
CONSTRAINT l_stakeholder_address_primarykey PRIMARY KEY (pk_l_stakeholder_address),
CONSTRAINT l_stakeholder_address_fk_stakeholder FOREIGN KEY (fk_stakeholder)
REFERENCES stakeholder (pk_stakeholder) MATCH SIMPLE
ON UPDATE CASCADE ON DELETE NO ACTION,
CONSTRAINT l_stakeholder_address_fk_address FOREIGN KEY (fk_address)
REFERENCES address (pk_address) MATCH SIMPLE
ON UPDATE CASCADE ON DELETE NO ACTION
)
WITH (
OIDS=FALSE
);
ALTER TABLE l_stakeholder_address OWNER TO postgres;
So far, no problem. Then I tried to add some values:
INSERT INTO individual (pk_stakeholder, fk_stakeholder_type, name, firstname, fk_title, email1, email2, phone1, phone2)
VALUES (1, 8, 'Lastname', 'Firstname', 1, 'me#you.com', '', '', '');
INSERT INTO address (pk_address, fk_gadmid_0, street, zip, city, public)
VALUES (1, 126, 'Address', '', 'City', FALSE);
INSERT INTO l_stakeholder_address (pk_l_stakeholder_address, fk_stakeholder, fk_address)
VALUES (DEFAULT, 1, 1);
And finally I end up having an error (SQL state 23503) saying that the key (fk_stakeholder)=(1) is not existing in table "stakeholder".
The first 2 inserts are fine, I can see them in the databases:
stakeholder:
pk_stakeholder | ...
----------------------
1 | ...
address:
pk_address | ...
--------------------
1 | ...
What am I doing wrong? I must admit that I am rather new to PostgreSQL (using 8.4) but I'm not even sure if that is an issue of PG at all, maybe I'm just lacking some basic database design understandings ...
Either way, by now I tried pretty much everything I could think of, I also tried to make the FK deferrable as in PostgreSQL : Transaction and foreign key problem but somehow that doesn't work either.
You can work around it using additional table individual_pks (individual_pk integer primary key) with all primary keys from both parent and child, which will be maintained using triggers (very simple — insert to individual_pks on insert, delete from it on delete, update it on update, if it changes individual_pk).
Then you point foreign keys to this additional table instead of a child. There'll be some small performance hit, but only when adding/deleting rows.
Or forget inheritance and do it the old way - simply one table with some nullable columns.
Your analysis is exactly right: It's because of the inheritance. When checking the foreign key, child tables are not considered.
In general, inheritance and foreign keys don't mix well in PostgreSQL. A major problem is that you can't have unique constraints across tables.
Reference