Sorry for asking something that has been mentioned a few times here but would like some help to get a better understanding. What I’m trying to do is be able to return a list of tags with the number of posts that has a tag associated with it.

    subquery = from(pt in PostTag, select: %{postCount: count(pt.tag_id)}, group_by: pt.tag_id)

    query =
      from(t in Tag,
        join: pt in subquery(subquery),
        on: t.id == pt.tag_id,
        where: ilike(t.name, ^search),
        select: %{id: t.id, name: t.name, count: pt.postCount},
        group_by: t.id
      )

We want to be able to return something like %{id: "1", count: 4} where the count is the number of posts associated with that tag. I currently have 3 tables, Post, Tag, and PostTags which connects the other two as many to many association.

I was hoping to get a better understanding of why I’m getting this error t0.id" must appear in the GROUP BY clause or be used in an aggregate function.

Thanks for the help and clarity in regards to this problem and pointing in the right direction in solving it.