How many repair assignments are there in file?
select count(*) from repair_assignment
Show me the name of technicians assigned to those repairs.
select t2.name from repair_assignment as t1 join technician as t2 on t1.technician_id = t2.technician_id
What about the series of machines they repaired?
select t3.name, t2.machine_series from repair_assignment as t1 join machine as t2 on t1.machine_id = t2.machine_id join technician as t3 on t1.technician_id = t3.technician_id