select r.rep_name, s.Rep_Cust_YTD from reps r, sales s
where r.rep_ID = s.rep_ID

select
  r.rep_name,
  s.Rep_Cust_YTD
from reps r
INNER JOIN sales s
  on r.rep_ID = s.rep_ID

select
  r.rep_name,
  SUM(s.Rep_Cust_YTD) Rep_YTD
from reps r
INNER JOIN sales s
  on r.rep_ID = s.rep_ID
GROUP BY r.rep_name

select r.rep_name, sum(s.Rep_Cust_YTD) as total
from reps r join sales s
on r.rep_ID = s.rep_ID
group by r.rep_name;