Example schema: http://sqlfiddle.com/#!1/3d410
I've already got a table and I want to add a new, not valid foreign key to the table. What's the correct syntax for adding a NOT VALID foreign key?
CREATE TABLE junks (
id serial PRIMARY KEY,
name text
);
CREATE TABLE trunks (
id serial PRIMARY KEY,
name text
-- no fk
);
-- and the below does not work!
--ALTER TABLE trunks ADD junk serial REFERENCES junks(id) NOT VALID;
You first add the column:
alter table trunks add column junk serial;
Then add the constraint to the table:
alter table trunks add constraint the_constraint_name
FOREIGN KEY (junk)
REFERENCES junks (id)
not valid;
This works:
ALTER TABLE trunks ADD CONSTRAINT FK_junk_id
FOREIGN KEY (id)
REFERENCES junks(id)
NOT VALID
;
See, e.g.: http://www.postgresql.org/docs/devel/static/ddl-alter.html#AEN2758
Related
I'm trying to define more than one foreign key in the process table. but I am getting the error that the columns I am trying to define as foreign key are not 'unique value'.
For this, I wanted to define id and name columns as primary keys in category and subject tables. However, when I want to create the process table, I still get this error." there is no unique constraint matching given keys for referenced table "category"
I have researched and continue to do so on Stackoverflow and many more. but I couldn't figure it out with solutions or viewpoints of the issues that got the same error I was facing. Maybe there is something I'm not seeing.
first table;
CREATE TABLE category(
category_id INT GENERATED ALWAYS AS IDENTITY,
category_name VARCHAR(210),
category_description TEXT,
CONSTRAINT category_pk PRIMARY KEY(category_id,category_name)
);
second table;
CREATE TABLE subject(
subject_id INT GENERATED ALWAYS AS IDENTITY,
subject_name VARCHAR(210),
subject_description TEXT,
CONSTRAINT subject_pk PRIMARY KEY(subject_id,subject_name)
);
I tried that too but I keep getting the same error
ALTER TABLE category ADD CONSTRAINT some_constraint PRIMARY KEY(category_id,category_name);
third table;
CREATE TABLE process(
process_id INT GENERATED ALWAYS AS IDENTITY,
fk_category_id INTEGER,
fk_subject_id INTEGER,
FOREIGN KEY(fk_category_id) REFERENCES category(category_id) ON DELETE CASCADE ON UPDATE
CASCADE,
FOREIGN KEY(fk_subject_id) REFERENCES subject(subject_id) ON DELETE CASCADE ON UPDATE
CASCADE
);
In your FOREIGN KEY declaration either:
Include both the columns that make up the PRIMARY KEY on category and subject e.g. ... REFERENCES category(category_id, category_name) ...
OR
Do not refer to any column and let the FK pick up the PK automatically e.g. ... REFERENCES category ON DELETE ....
I am going to say that what you are really after is:
CREATE TABLE category(
category_id INT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
category_name VARCHAR(210) UNIQUE,
category_description TEXT
);
CREATE TABLE subject(
subject_id INT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
subject_name VARCHAR(210) UNIQUE,
subject_description TEXT
);
CREATE TABLE process(
process_id INT GENERATED ALWAYS AS IDENTITY,
fk_category_id INTEGER,
fk_subject_id INTEGER,
FOREIGN KEY(fk_category_id) REFERENCES category ON DELETE CASCADE ON UPDATE
CASCADE,
FOREIGN KEY(fk_subject_id) REFERENCES subject ON DELETE CASCADE ON UPDATE
CASCADE
);
An identity column isn't automatically a primary key. So your tables category and subjectdon't have any primary keys and thus can't be referenced by a foreign key.
You need to add PRIMARY KEY to the columns of the tables category and subject
I created this first table named 'bookstore' where Primary Key is book_name:
create table bookstore (book_name varchar primary key, author varchar, price decimal);
I am trying to create a second table named 'name' where name is primary key. I want to make this primary key- author.name as a foreign key of bookstore.author.
create table author (name varchar primary key, place varchar,
constraint fk_author_bookstore foreign key(name) references bookstore(author));
But the error is: ERROR: there is no unique constraint matching given keys for referenced table "bookstore"
SQL state: 42830
I am new to SQL, so, hoping to get some help. If you can, please write the correct code.
Thanks
Name column in author table is primary key and it's referenced as foreign key in bookstore table.
-- PostgreSQL (v11)
create table author (name varchar primary key, place varchar);
create table bookstore (book_name varchar primary key, author varchar, price decimal
, CONSTRAINT fk_author_bookstore
FOREIGN KEY(author)
REFERENCES author(name));
Please check from url https://dbfiddle.uk/?rdbms=postgres_11&fiddle=8394f796433ed8bc170c2889286b3fc2
Add foreign key after table creation
-- PostgreSQL(v11)
ALTER TABLE bookstore
ADD CONSTRAINT fk_author_bookstore FOREIGN KEY (author)
REFERENCES author (name);
Please check from url https://dbfiddle.uk/?rdbms=postgres_11&fiddle=d93cf071bfd0e3940dfd256861be813c
What is the equivalent of this in postgresql ?
--
-- Index for the table `Artist`
--
ALTER TABLE `Artist`
ADD PRIMARY KEY (`idArtist`),
ADD UNIQUE KEY `name` (`name`,`firstName`);
ADD KEY `idFilm` (`idFilm`);
Adding a primary key is the same.
alter table artist
add primary key (idartist);
For the unique constraint you have two choices:
alter table artist
add constraint name unique (name, firstname);
or a unique index:
create unique index name on artist (name, firstname);
I think the key thing, simply adds a regular index:
create index idfilm on artist (idfilm);
I'm working on a project for which I want to use inheritance (see code below)
When I try to insert something into Profile there is an error.
ERROR: insert or update on table "profile" violates foreign key
constraint "profile_id_fkey"
DETAIL: Key (id)=(21) is not present in table "test".
I'm using PSequel to inspect the database and the values are visible in the parent. However, I am still able to insert a duplicate primary key in the parent. The insert then works.
CREATE TABLE Test (
ID INTEGER NOT NULL,
PRIMARY KEY (ID)
);
CREATE TABLE Testchild (
PRIMARY KEY (ID)
) INHERITS (Test)
;
CREATE TABLE Profile (
ProfileID INTEGER NOT NULL,
ID INT NOT NULL,
PRIMARY KEY (ProfileID)
);
ALTER TABLE Profile
ADD FOREIGN KEY (ID) REFERENCES Test(ID);
INSERT INTO Testchild VALUES (21);
INSERT INTO Profile VALUES (1,21);
From PostgreSQL documentation:
A serious limitation of the inheritance feature is that indexes (including unique constraints) and foreign key constraints only apply to single tables, not to their inheritance children. This is true on both the referencing and referenced sides of a foreign key constraint. Thus, in the terms of the above example:
https://www.postgresql.org/docs/9.1/static/ddl-inherit.html
So you have to declare explicitly any FK, they wont inherit
I have a table in postgresql with a composite primary key. The primary key consists of two columns named:
DATETIME, UID
I have a another (non-null) column named ACTION already existing in this table. How do I add ACTION to the composite primary key? Ie: I'd like the resulting primary key of the table to be the triplet:
DATETIME, UID, ACTION
First drop the primary key constraint. You can get the name of the constraint by typing
\d my_table
and look under indexes for something like:
"my_table_pkey" PRIMARY KEY, btree (datetime, uid)
Drop it by doing:
alter table my_table drop constraint my_table_pkey;
Then create the new composite primary key by doing:
alter table my_table add constraint my_table_pkey primary key (datetime, uid, action);