GATE 2024 Databases Rank Booster Quiz 40

Consider the following relation schema and SQL query:

Which of the following is return by the above SQL query?

For what values of x and y, including NULL, does the Boolean expression x ≤ 3 AND Not (y ≥ 1) have the truth value UNKNOWN in SQL?

Which of the following is correct about SQL?

Consider the following relation schema Instructor (ID, Name, Dept_name, Salary) with table:

Consider the following SQL query:

SELECT Dept_name, avg_salary

FROM (SELECT Dept_name, avg (salary) as avg_salary

FROM instructor

GROUP by Dept_name)

WHERE avg_salary > 42000;

The number of tuple returned by the above SQL query is ________.

Consider the following statements:

S₁: Select operation in SQL is equivalent to the projection operation in relational algebra, except that
select SQL contain duplicates.
S₂: A SQL query can have a ‘having’ clause without containing ‘group by’ clause.
S₃: Operator ‘between’ can be used between main query and the sub query.
S₄: If two relations R and S are joined, then the non-matching tuples of both R and S are ignored in full outer join.

Which of the above statements are correct?

Consider the following relation schema:

Employee (emp-name, street, city)

Work (emp-name, company-name, salary)

Company (company-name, city)

Manages (emp-name, manager-name)

What does the following query return?

Select a.emp-name

From employee a, employee b, managers m

Where a.emp-name = m.emp-name and m.manager-name = b.emp-name

and a.street = b street and a.city = b.city;

EMPLOYEE (Fname, Lname, Eno, Bdate, Address, Sex, Salary, Superssn dno)

DEPENDENT (Eno, DFname, DLname, Age)

What is true about these queries?

Query 1:

Query 2: