I'm testing the pagila (the postgres port of mysql sakila sample).
Well, I was trying to translate the query:
select
film.film_id AS FID,
film.title
AS title,
film.description AS description,
category.name AS category,
film.rental_rate AS price,
film.length AS length,
film.rating AS rating,
group_concat(concat(actor.first_name,_utf8' ',actor.last_name) separator ',') AS actors
from
category
inner join film on(category.category_id = film.category_id)
inner join film_actor on(film.film_id
= film_actor.film_id)
inner join actor on(film_actor.actor_id = actor.actor_id)
group by
film.film_id;That cant be find here: http://www.stardata.it/articoli_en/mysql_sample_db_articoli_en.html
I read a comment by David Fetter on a blog about group concat. I'm following his example:
select
film.title AS title,
array_to_string(array_accum( actor.first_name || ' ' || actor.last_name),',') AS actors
from
film
inner join film_actor on film.film_id = film_actor.film_id
inner join actor on film_actor.actor_id = actor.actor_id
GROUP BY film.title
But, when I add another column on select, like, film_description, I get the following error:
"ERROR: column "film.description" must appear in the GROUP BY clause or be used in an aggregate function"
If I put that column on GROUP BY everything works ok. But I want understant why do I need to do that. Can someone teach me, please?
[]'s
- Walter
