The following queries produce the same results.
select customer_name,customer_city
from customer,salesman
where customer.salesman_id = salesman.salesman_id
and salesman.lname = 'SMITH';
select customer_name,customer_city
from customer
where customer.salesman_id =
(select salesman_id
from salesman
where lname = 'SMITH');

Question

Quizplus · Accepted Answer

Both queries retrieve the customer name and city for customers who are assigned to salesman with the last name 'SMITH'. The first query achieves this by joining the customer and salesman tables on the salesman_id column and filtering for salesman with the last name 'SMITH'. The second query achieves this by using a subquery to select the salesman_id for salesman with the last name 'SMITH', and then selecting the customer name and city for customers with that salesman_id.

The Following Queries Produce the Same Results