Could you please show me the ids of the projects with at least 2 documents?
select project_id from documents group by project_id having count ( * ) > = 2
What about those with at least 3 documents?
select project_id from documents group by project_id having count ( * ) > = 3
What are the dates of those, please?
select project_id,document_date from documents group by project_id having count ( * ) > = 3
Yes
select document_date from documents where project_id in ( select project_id from documents group by project_id having count ( * ) > = 3 )
What are the project ids of those?
select project_id from documents group by project_id having count ( * ) > = 3