How to add Foreign key constraint on array in PostgreSQL?

Question

look_up table for roles

CREATE TABLE party_role_cd
(
  party_role_cd bigint NOT NULL,
  code character varying(80) NOT NULL,
  CONSTRAINT party_role_cd PRIMARY KEY (party_role_cd)
);

Party can have zero or many roles [ 0-N relationship ]

CREATE TABLE party
(
  party_id biging NOT NULL,
  party_role_cd bigint[] NOT NULL,
  CONSTRAINT party_id PRIMARY KEY (party_id)
);

How to add the foreign key constraint for party_role_cd array in party table?

This is not possible. Normalise the schema and use a separate table. — Bergi
– Bergi, Commented Aug 6, 2020 at 2:00

Erwin Brandstetter · Accepted Answer · 2020-08-06 23:42:26Z

6

That's not implemented in PostgreSQL. Currently, FK constraints only operate on equality between whole column values. No array-to-element references. There is an open TODO item that has been added in 2010. See:

There were even attempts to implement it, but never to completion.

edited Aug 6, 2020 at 23:42

answered Aug 6, 2020 at 2:38

Erwin Brandstetter

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2 Comments

Cpp crusaders Over a year ago

i had a similar Problem. I am thinking if I have a table: id (serial), array(Integers[]) then I Will have a seperate table: id_of_table1, array_element (Integer) Table 1 & table 2 are always in sync through insert/update/delete Triggers. Now array_element is a foreign key of another table. In addition I need to make sure each array has unique elements.. I can achieve that by Unique Index on id_of_table1, array_element

Cpp crusaders Over a year ago

basically a variation of stackoverflow.com/questions/8016776/… but uniqueness is Per array in each Row and not throughout the table

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