6. What question does this correlated query answer? Begin your answer with “This query answers the question: which customers…” SELECT customer_id, first_name, last_nameFROM customers cWHERE NOT EXISTS( SELECT *  FROM orders o  WHERE o.customer_id = c.customer_id)ORDER BY first_name, last_name;

4. Find the movies that are the only movie released by a director (In other words, show the movies where the director has directed only one movie). Hint: Subquery is needed

1. Find the names of all reviewers who have provided ratings for movies, listed without any duplicates.

9. What are three advantages of using views?

Suppose D is a  4×6 matrix and S is a pxq matrix. Suppose we want to compute the product DS. Which is true?

What is the largest possible rank of a 7×3 matrix?

We know matrix multiplication does not commute in general. However, there are statements we can make in specific situations related to commutativity.    Determine whether each statement is true or false. 

A group of students is working on a puzzle. Each student has two pieces necessary to complete it. All the students need to complete the puzzle. This situation is an example of a(n) ________________. [BLANK-1]

Tereza believes that all Asians are good in math. This belief is an example of a(n)________________. [BLANK-1]

Explain what is meant by the contact hypothesis.