SQL allows duplicate tuples in relations, and correspondingly defines the multiplicity of tuples in the result of joins. Which one of the following queries always gives the same answer as the nested query shown below:

Select * from R where a in (select S.a from S)

Consider the following relational schema:

employee (empId, empName, empDept )

customer (custId, custName, salesRepId, rating)

SalesRepId is a foreign key referring to empId of the employee relation. Assume that each employee makes a sale to at least one customer. What does the following query return?

SELECT empName 
FROM employee E 
WHERE NOT EXISTS (SELECT custId 
       FROM customer C 
       WHERE C.salesRepId = E.empId 
       AND C.rating <> 'GOOD');

Given the following schema:

employees(emp-id, first-name, last-name, hire-date, dept-id, salary)

departments(dept-id, dept-name, manager-id, location-id)

You want to display the last names and hire dates of all latest hires in their respective departments in the location ID 1700. You issue the following query:

SQL> SELECT last-name, hire-date 
FROM employees WHERE (dept-id, hire-date) IN 
(SELECT dept-id, MAX(hire-date) 
FROM employees JOIN departments USING(dept-id) 
WHERE location-id = 1700
GROUP BY dept-id);

What is the outcome?

Consider the following relational schema.

Students(rollno: integer, sname: string)

Courses(courseno: integer, cname: string)

Registration(rollno: integer, courseno: integer, percent: real)

Which of the following queries are equivalent to this query in English?

"Find the distinct names of all students who score more than 90% in the course numbered 107"

(I) SELECT DISTINCT S.sname 
FROM Students as S, Registration as R 
WHERE R.rollno=S.rollno AND 
R.courseno=107 AND R.percent >90

(II) ∏_sname(σ_courseno = 107 ∧ percent > 90 (Registration ⋈ Students))

(III) { T | ∃S ∈ Students, ∃R ∈ Registration ( S.rollno=R.rollno ∧ R.courseno=107 ∧ R.percent > 90 ∧ T.sname=S.sname)}

(iv) { < S_N >| ∃S_R∃R_P ( < S_R, S_N > ∈ Students ∧ ∈ Registration ∧ R_P > 90)}