Find the id of the architect who built each bridge.
select architect_id from bridge
How many bridges did each one build?
select count(*) from bridge group by architect_id
What are the ids and names of those who built at least 3 bridges ?
select t1.id, t1.name from architect as t1 join bridge as t2 on t1.id = t2.architect_id group by t1.id having count(*) >= 3