LATERAL queries allow you to select more than one column and one row in a correlated subquery. This is very useful when creating Top-N subqueries and trying to join table functions together, thus making unnesting them a clear possibility. The LATERAL query can then be thought of as a sort of SQL foreach loop.
Let's give a simple example that would illustrate how a LATERAL query would work. Let's say that we have two hypothetical tables that contain data on films and actors:
SELECT film.id, film.title, actor_bio.name, actor_bio.biographyFROM film, LATERAL (SELECT actor.name, actor.biography FROM actor WHERE actor.film_id = film.id) AS actor_bio;
As we can see, the LATERAL subquery is selecting multiple columns from the actor ...
