5th sem r2 final

Which SQL statement adds a UNIQUE constraint to a column email in the users table?

• ALTER TABLE users ADD CONSTRAINT UNIQUE(email);

• ALTER TABLE users ADD UNIQUE(email);

• CREATE UNIQUE email ON users;

• ADD CONSTRAINT UNIQUE TO users.email;

How do you filter rows where age is between 25 and 40 but exclude ages 30 and 35?

• SELECT * FROM table WHERE age BETWEEN 25 AND 40 AND age NOT IN (30, 35);

• SELECT * FROM table WHERE age BETWEEN 25 AND 40 OR age NOT BETWEEN 30 AND 35;

• SELECT * FROM table WHERE age IN (25, 26, ... 40) EXCEPT (30, 35);

• SELECT * FROM table WHERE age BETWEEN 25 AND 40 AND age IS NOT (30, 35);

Which method allocates IPs efficiently across a network with limited public IPs?

• Subnetting

• Network Address Translation (NAT)

• Classful Addressing

• Static IP Allocation

Which transport-layer protocol is best for real-time gaming to minimize delay?

• TCP

• UDP

• ICMP

• SCTP

Which query retrieves names of employees whose salaries are higher than the department average?

• SELECT name FROM employees WHERE salary > (SELECT AVG(salary) FROM employees);

• SELECT name FROM employees WHERE salary > AVG(salary) GROUP BY department;

• SELECT name FROM employees WHERE salary > DEPT_AVG(salary);

• SELECT name FROM employees WHERE salary > ALL (SELECT salary FROM employees);

Which feature of IPv4 allows splitting packets for smaller MTU links?

• Address Aggregation

• Subnetting

• Fragmentation

• Packet Switching

How does CSMA/CA ensure collision avoidance?

• By sending acknowledgment packets after data transmission

• By broadcasting 'ready-to-send' and 'clear-to-send' signals

• By detecting and delaying retransmissions upon collision

• By allowing devices to take fixed transmission slots

What does the Durbin-Watson statistic close to 0 indicate?

• Positive autocorrelation

• Negative autocorrelation

• No autocorrelation

• Strong multicollinearity

Which query returns the top 3 highest salaries from an employees table?

• SELECT salary FROM employees ORDER BY salary DESC LIMIT 3;

• SELECT TOP 3 salary FROM employees ORDER BY salary;

• SELECT salary FROM employees WHERE RANK <= 3;

• SELECT salary FROM employees WHERE salary >= MAX(salary);

What is the main advantage of using a candidate key over a composite key?

• Faster indexing due to fewer fields

• Increased data redundancy

• Easier normalization

• Enforcing referential integrity