A DBA adds an index and moves a table to a faster disk, and no application program or conceptual schema has to change. Which property does this demonstrate?
Correct answer D. Physical data independence
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DBMS and SQL MCQs
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Table Emp(id, dept, salary) has rows (1,’HR’,3000), (2,’IT’,5000), (3,’IT’,4000), (4,’Ops’,2000). SELECT dept FROM Emp GROUP BY dept HAVING MAX(salary) – MIN(salary) > 0; What is returned?
Correct answer D. IT
Table Colour(c) has rows ‘red’, ‘blue’. Table Size(s) has rows ‘S’, ‘M’, ‘L’. SELECT COUNT(*) FROM Colour CROSS JOIN Size; What is the result?
Correct answer C. 6
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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?
Correct answer A. 5, 4
Table Marks(score) has rows 40, 50, 60, 70 and 80. SELECT COUNT(*) FROM Marks WHERE score BETWEEN 50 AND 70; What is returned?
Correct answer B. 3
Table Student(name) has rows ‘amir’, ‘asma’, ‘bilal’, ‘sana’ and ‘aamna’. SELECT COUNT(*) FROM Student WHERE name LIKE ‘a_m%’; What is the result?
Correct answer C. 2
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?
Correct answer D. 3
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?
Correct answer B. Only (IT, 9000)
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?
Correct answer D. 3000
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