[Slick 2.0]: How to translate subqueries from sql to Slick

Question

I have the following (mysql) SQL query:

select a.id, a.name, count(*) as humans
from humans h1, areas a
where h1.gender = 'Female' and h1.area_id = a.id
group by area_id
having count(*) > (
    select count(*)
    from humans h2
    where h2.gender = 'Male' and h1.area_id = h2.area_id
    group by area_id
    )
    or not exists (
    select *
    from humans h2
    where gender = 'Male' and h1.area_id = h2.area_id
    group by area_id
)

Which basically shows all the areas which are dominated by female humans.

How exactly would I translate this to the slick syntax?

I am not quiet sure from the examples on the site how to use subqueries with correlations.

Answer 1

If you have such a big query and you doubt this would be changed in future, I'd recommend using Slick Plain SQL API because of 2 reasons:

• it is easier to implement
• some sort it's easier to support - cleaner view

Of course you'll loose compiler's time safety, but this might be non-critical if you are not going to change the query too often.

So the result would be:

  Database.forURL("jdbc:h2:mem:humans", driver = "org.h2.Driver") withSession { implicit session =>

    val sql = """
    select a.id, a.name, count(*) as humans
    from humans h1, areas a
    where h1.gender = 'Female' and h1.area_id = a.id
    group by area_id
    having count(*) > (
        select count(*)
        from humans h2
        where h2.gender = 'Male' and h1.area_id = h2.area_id
        group by area_id
        )
        or not exists (
        select *
        from humans h2
        where gender = 'Male' and h1.area_id = h2.area_id
        group by area_id
    )
    """

    val result: (Long, String, Long) = StaticQuery.queryNA[(Long, String, Long)](sql).first()

    //do something with the result
  }