How to write a recursive function in PostgreSQL?

Question

PHP

How to write a recursive function?
The function input is the movie id and the result is all the prequels for the movie.

spoiler

Here is my version of the function, only it outputs all movies.

spoiler

create or replace function get_all_prequils(filmid int)
returns table (id int, filmname varchar, prequelid int) as $$
  with recursive rec as (
  select f.FilmID, f.FilmName, f.PrequelID
  from Film as f
  where f.FilmID = filmid
    
  union
  
  select r.FilmID, r.FilmName, r.PrequelID
    from rec as r
  join Film f on f.PrequelID = r.FilmID
)
select *
from rec
$$ language sql;

select get_all_prequils(1);

spoiler

Answer 1

(?<!^)(\p{Lu})/gumreplace with " $1"(space at the beginning)
https://regex101.com/r/nM45ZQ/1
Demo: https://ideone.com/cSH2eU

Answer 2

https://habr.com/ru/post/269497/

Answer 3

Here vvs.ru/pg a person regularly builds pgAdmin 3 for new versions. At the moment, everything works without errors with PostgreSQL version 12.1