![]() You can make it a bit more efficient and add more rules depending on your requirements. Trailer=# insert into combine values (1,'') ĮRROR: insert or update on table "donkey" violates foreign keyĭETAIL: Key (others)=(3) is not present in table "harvester". A foreign key constraint, also known as Referential integrity Constraint, specifies that the values of the foreign key correspond to actual values of the primary key in the other table. PostgreSQL FOREIGN KEY example Let us consider two tables vendors and to illustrate the FOREIGN KEY in PostgreSQL. (delete from donkey where donkey.id=new.id insert into donkey select A foreign key constraint, also known as Referential integrity Constraint, specifies that the values of the foreign key correspond to actual values of the primary key in the other table. Trailer=# create rule combine_insert as on insert to combine do instead Trailer=# create view combine as select id, array_agg(others) as others Trailer=# create unique index donkey_ears on donkey (id, others) Trailer=# create table donkey (id int, others int references Trailer=# insert into harvester values (1,'grain'), (2,'cricket') ![]() Here is how: trailer=# create table harvester (id int unique, label text) I then made it possible to insert into the view by adding an appropriate rule. ![]() The user table was then a view of the hidden table with all the roles assembled into an array. Essentially I made a hidden table that contained one row for each (user,role) pair with suitable constraints. I just made something similar for a colleague.
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