Question

I have two classes

Quiz{
  String name
  static hasMany[tags:Tag]
}

Tag{
    String tag
}

How can I write the following query in grails using criteria builder

select count(tag_id),tag  from quiz_tag 
left outer join tag on tag_id=id
group by tag_id,tag

Answer 1

You could do this with a criteria query if you map the many-to-many table with a domain class, like explained here.

class QuizTag {
    Quiz quiz
    Tag tag

    ...
}

def counts = QuizTag.withCriteria {
    projections {
        groupProperty('tag')
        rowCount()
    }
}

The counts variable will be a List of [Tag object, count of the Tag] lists.