Practice mode DBMS and SQL

Table Pay(id, salary, bonus) has one row (1, 5000, NULL). SELECT salary + bonus FROM Pay; What is returned?

Correct answer A. NULL

Explanation

In SQL, an arithmetic expression with a NULL operand yields NULL, because NULL means an unknown value and an unknown added to 5000 is still unknown. The result is not 5000; NULL is not treated as zero in expressions. Aggregates such as SUM skip NULLs, but row-level arithmetic does not. Write salary + COALESCE(bonus, 0) to treat a missing bonus as zero.

Report a problem

Answer checked 12 October 2026 How we write and check questions

Tip: press A, B, C or D to answer, and N for the next question.

Table Pay(id, salary, bonus) has one row (1, 5000, NULL). SELECT salary + bonus FROM Pay; What is returned?

Discussion

Have a question about this answer? Cancel reply

Table Pay(id, salary, bonus) has one row (1, 5000, NULL). SELECT salary + bonus FROM Pay; What is returned?

More DBMS and SQL questions

Table Emp(id, dept, salary) has rows (1,’HR’,3000), (2,’IT’,5000), (3,’IT’,4000), (4,’HR’,NULL), (5,’Ops’,2000). SELECT COUNT(*), COUNT(salary) FROM Emp; What does this query return?

Table Emp(id, dept, salary) has rows (1,’HR’,3000), (2,’IT’,5000), (3,’IT’,4000), (4,’HR’,NULL), (5,’Ops’,2000). SELECT AVG(salary) FROM Emp WHERE dept = ‘HR’; What value is returned?

Table Emp(id, dept, salary) has rows (1,’HR’,3000), (2,’IT’,5000), (3,’IT’,4000), (4,’HR’,NULL), (5,’Ops’,2000). SELECT dept, SUM(salary) FROM Emp GROUP BY dept HAVING SUM(salary) > 3000 ORDER BY dept; Which rows are returned?

Table Emp(id, dept, salary) has rows (1,’HR’,3000), (2,’IT’,5000), (3,’IT’,4000), (4,’HR’,NULL), (5,’Ops’,2000). SELECT COUNT(DISTINCT dept) FROM Emp; What is the output?

Discussion

Have a question about this answer? Cancel reply