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Class 12 · Computer Science worksheetDatabase Concepts
CBSE Computer Science. File system and DBMS, the relational model: relation, attribute, tuple, domain, degree and cardinality; candidate, primary, alternate and foreign keys. Every sheet has 20 questions in three sections and an answer key, and the questions change every time.
Sample questions
Real questions from this chapter, as the app sets them. Tap Answer to see the answer and working.
Section A · multiple choice
- 1.
In the relational model, a table is called a:
- domain
- schema key
- tuple
- relation
Answer
(d) relation
- 2.
Table: STUDENT RollNo | Name | Sec | City | Marks 101 | Dev | C | Delhi | 47 102 | Ananya | A | Delhi | 58 103 | Zoya | B | Delhi | 92 104 | Isha | B | Delhi | 46 105 | Vikram | C | Indore | 68 106 | Rahul | C | Pune | 40 107 | Priya | C | Delhi | 96 108 | Kabir | A | Indore | 83 What is the cardinality of this relation?
- 7
- 8
- 5
- 9
Answer
(b) 8
8 tuples (rows); the heading is not a tuple
- 3.
Relation R has degree 5 and cardinality 3; relation S has degree 4 and cardinality 4. What is the degree of their Cartesian product R × S?
- 7
- 8
- 20
- 9
Answer
(d) 9
5 + 4: every attribute of both
Section B · short answer
- 4.
Give two limitations of keeping data in a file system instead of a database.
Answer
Data redundancy (the same data in many files) and inconsistency; also difficulty of access, data isolation and weak control over who sees the data.
- 5.
Table: EMPLOYEE EmpNo | Name | Dept | Salary | Bonus E1 | Vikram | IT | 42000 | 4000 E2 | Dev | HR | 64000 | NULL E3 | Meera | IT | 57000 | 2000 E4 | Ananya | IT | 51000 | 6500 E5 | Priya | IT | 49000 | NULL E6 | Asha | HR | 76000 | NULL Write (a) the degree and (b) the cardinality of this relation.
Answer
(a) 5; (b) 6
degree = number of attributes; cardinality = number of tuples
Section C · long answer
- 6.
Explain the limitations of a file system that a database management system overcomes.
Answer
A file system repeats data in many files (redundancy), so copies disagree (inconsistency); data is hard to combine across files (isolation), each new query needs a new program (difficult access), and controlling who may see what is weak. A DBMS stores data once, keeps it consistent, answers queries in SQL and controls access.
Fresh sheets for your child
In the app, every Database Concepts sheet is new: the app remembers the questions your child has already had and leaves them out. Print the sheet as a PDF, or use notebook mode and write the answers in a notebook.
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