Assuming that we have 2 tables - customers and orders:

Which of the following queries is correct to count the customers who have put at least one order?

Assuming that we have 2 tables - customers and orders:

Assume also that we have 2 customers and the first customer has 3 orders and the second customer has 5 orders. How many rows will the following select query bring?

select * from customers join orders on orders.customer_id = customers.customer_id;

PostgreSQL  supports inner join, left join, right join, full outer join, cross join, natural join, and a special kind of join called self-join.

Match the type of join and the appropriate purpose of usage (PostgreSQL).

If the rows in the joined table do not match, the full outer join sets values for every column of the table that does not have the matching row.

When you want to use a join between columns that are in the same table, you use what type of join?

Which JOIN returns the Cartesian product of the two tables?

We use  to combine the result set of two or more SELECT statements

Which JOIN returns ...

(match the appropriate)

What is a JOIN in a relational DBMS?