My version:
select
c.cust_nam, count(s.qty_sold) as cust_qty_sold
from customers c, sales s
where
c.cust_id = s.cust_id and
s.sale_dat >= ‘20100101’and
s.sale_dat <= ‘20101231’
group by c.cust_nam
errors are
1. Wrong: count s.qty_sold
Correct: count(s.qty_sold)
2. Wrong: from customers c and sales s
Correct: "from customers c, sales s
3. Wrong: c.cust_id = s.cust_id,
s.sale_dat >= ‘20100101’,
s.sale_dat <= ‘20101231’
Correct: c.cust_id = s.cust_id and
s.sale_dat >= ‘20100101’and
s.sale_dat <= ‘20101231’
