[cpburns2009]

I think PostgreSQL makes this the clearest because it supports arrays:

    SELECT
      movie.id,
      movie.name,
      array_remove(array_agg(producer.last_name), NULL) AS last_names
    FROM movie
    LEFT JOIN producer ON movie.id = producer.movie_id
    GROUP BY
      movie.id,
      movie.name;

[MarkusWinand]

Just FYI: starting with 9.4, PostgreSQL supports the FILTER clause. This would change this:

> array_remove(array_agg(producer.last_name), NULL) AS last_names

to that

> array_agg(producer.last_name) FILTER(WHERE producer.last_name IS NOT NULL) AS last_names

I wrote about FILTER here: http://modern-sql.com/feature/filter

And how to use ARRAYs rather than concatenated strings here: http://modern-sql.com/feature/listagg#alternative-array

[cpburns2009]

I wasn't aware of that feature. Now I really need to push for upgrading PostgreSQL to a newer version.