MIDTERM FUNDAMENTALS OF DATABASES GEN 11

A UNION query is which of the following? A UNION query is which of the following?

• Combines the output from two queries and must include the same number of columns
• Combines the output from multiple queries and must include the same number of columns
• Combines the output from multiple queries and does not have to include the same number of columns
• Combines the output from two queries and does not have to include the same number of columns

In the given query which of the keywords has to be inserted?

• Value
• Field
• Relation
• Table

Which of the following relations is in Third normal form (3NF)?

• R(ABCD) FD’s: AB -> C; BCD -> A; D -> A; B -> C
• R(ABCD) FD’s: C -> B; B -> A; AC -> D; AC -> B
• R(ABCD) FD’s: ACD -> B; AC -> D; D -> C; AC -> B
• R(ABCD) FD’s: AB -> C; ABD -> C; ABC -> D; AC -> D

Which of the following is NOT true about SQL Subqueries?

• Subqueries are executed first.
• None of these.
• They are nested queries.
• Only one subquery can be nested.

This graphic indicates: Select one:

• -a student cannot own a car.
• that a student can own 0,1 or many cars.
• A car can be owned by many students
• A student can own many cars and a car can be owned by many students

Which of the following statements is NOT true about subqueries?

• Subqueries may occur in other places than the WHERE clause.
• Subqueries can be added with an ORDER BY clause.
• Subqueries cannot be nested multiple times
• Subqueries can be used to compare an expression to the result of the query

Suppose relations R(A, B) and S(B, C, D) are as follows: Compute the full outer join on B, the left outer join on B, and the right outer join on B. In each case, R is the left operand and S is the right operand. Find the correct statement in the list below.

• The full outer join has 3 NULL’s
• The full outer join has 6 tuples
• The full outer join has 3 tuples
• The full outer join has 2 NULL’s

In ERD, what is the meaning of the rounded arrow?

• A. One or many
• B. Many
• C. One and only one
• D. One or Zero

Supposed we have a table staffs containing the first and last name of all staffs in USTH. Write a query to return find the official email of each person, given that the domain is @usth.edu.vn and the mail is of the following format: [e-mail]

• A. SELECT first_name, last_name, concat(last_name, ‘.’, first_name, ‘@usth.edu.vn’) AS Official_mail FROM Staffs
• B. SELECT first_name, last_name, concat(last_name, ‘.’, first_name) AS Official_mail FROM Staffs;
• C. All of these are correct
• D. SELECT first_name, last_name, distinct(first_name) AS Official_mail FROM Staffs;

Supposed we have a table Employee that contains the id (emp_id), name(emp_name) and working experience (experience) of each employee in a company. Write a query to find the second employee in terms of experience in increasing order? (first being the one with max experience).

• A. SELECT emp_id, MAX(experience) AS second_max_exp FROM Employee WHERE experience < (SELECT MAX(experience) FROM Employee);
• B. All are correct
• C. SELECT emp_id, experience AS second_max_exp FROM Employee WHERE experience < (SELECT MAX(experience) FROM Employee);
• D. SELECT emp_id, experience AS second_max_exp FROM Employee WHERE experience > (SELECT MAX(experience) FROM Employee);