DATABASE MANAGEMENT SYSTEMS Two marks for unit 3

Anna University  DATABASE MANAGEMENT SYSTEMS Two marks for unit 3

UNIT III

1. Define Boyce codd normal form
A relation schema R is in BCNF with respect to a set F of functional
+dependencies if, for all functional dependencies in F of the form

2. List the disadvantages of relational database system
Repetition of data
Inability to represent certain information.

3. What is first normal form?
The domain of attribute must include only atomic (simple, indivisible) values.

4. What is meant by functional dependencies?
Consider a relation schema R and a
C
R and ß
C
R. The functional dependency a
ß
holds on relational schema R if in any legal relation r(R), for all pairs of
tuples t1 and t2 in r such that t1 [] =t1 [], and also t1 [[1]] =t2 [[1]].

5. What are the uses of functional dependencies?
To test relations to see whether they are legal under a given set of functional
dependencies.
To specify constraints on the set of legal relations.

6. Explain trivial dependency?
Functional dependency of the form a
ß
is trivial if ß
C
. Trivial functional
dependencies are satisfied by all the relations.

7. What are axioms?
Axioms or rules of inference provide a simpler technique for reasoning about
functional dependencies.

8. What is meant by computing the closure of a set of functional dependency?
The closure of F denoted by F+ is the set of functional dependencies logically
implied by F.

9. What is meant by normalization of data?
It is a process of analyzing the given relation schemas based on their Functional
Dependencies (FDs) and primary key to achieve the properties
Minimizing redundancy
Minimizing insertion, deletion and updating anomalies.

10. Define canonical cover?
A canonical cover Fc for F is a set of dependencies such that F logically implies
all dependencies in FC and Fc logically implies all dependencies in F. Fc must
have the following properties.

11. List the properties of canonical cover.
Fc must have the following properties.
No functional dependency in Fc contains an extraneous attribute.
Each left side of a functional dependency in Fc is unique.

12. Explain the desirable properties of decomposition.
Lossless-join decomposition
Dependency preservation
Repetition of information

13. What is 2NF?
A relation schema R is in 2NF if it is in 1NF and every non-prime attribute A in R
is fully functionally dependent on primary key.

14.Define 1NF

• Tabular format in which:
• All key attributes are defined
• There are no repeating groups in the table
• All attributes are dependent on primary key
• All relational tables must satisfy 1NF requirements

15. How to convert to First Normal Form

A table in a relational database must be in 1NF.

• Repeating groups must be eliminated
• Primary key determined
• Uniquely identify attribute values (rows)
• All attributes dependent on primary key
• In example: Combination of PROJ_NUM and EMP_NUM

16.What is Dependency diagram?

• Dependency diagram:
• Depicts all dependencies found within a given table structure
• Helpful in getting bird’s-eye view of all relationships among a table’s attributes
• Use makes it much less likely that an important dependency will be overlooked

17.What are the Desirable dependencies based on entire primary key
Partial:
Based on part of composite primary key
Transitive:
One nonprime attribute depends on another nonprime attribute

18.What are the aspects to be considered to check Table is in second normal form (2NF)?
Table is in second normal form (2NF) if:
ü  It is in 1NF and
ü  It includes no partial dependencies:
ü  No attribute is dependent on only a portion of the primary key

19.Define Physical Data Independence:
            The execution of application programs is not affected by the changes in the physical data access and storage methods.

20.Define Logical Data Independence:
            Logical changes in tables and views such as adding/deleting columns or changing field length need not necessiatitate modifications in the programs. The database can change and grow to reflect changes in reality without requiring the user intervention or changes in the applications.

PART B

1. Discuss concept of database language
2. Discuss about database interfaces.
3. What is relationship ? What are various types of relationship ? Explain with example.
4. Explain the Codd’s Rule in detail.
5. What do you mean by RDBMS ? What are its characteristics ?
6. Explain Entity integrity and Referential integrity in detail.
7. What is the difference between DBMS and RDBMS ? Which of them is more suitable?
8. What is relational algebra ? Discuss the various operations of relational algebra.
9. Describe the different types of relational calculus in detail.
10.What dis relational calculus ? Differentiate relational algebra and relational calculus.
11. What do you mean by Null values? Explain with suitable examples.
12. Why normalization needed ? What are its disadvantages ?
13..Discuss the various normal form in normalization with suitable examples.
14. Define term anomalies.Explain BCNF in detail.
15.What do you mean by BCNF ? Why it is used and how it differ from 3 NF ?
16. Explain the different normal forms in detail
17.Explain Functional dependency and Trivial functional dependency with examples.
18.Explain Fourth normal forms with examples.
19.Explain Closure of Set of Functional dependency and Closure of Attribute sets
20.Explain Canonical cover and Extraneous Attributes with examples.
21.Explain BCNF with examples and also state the difference between this from 3NF.
22. Give the various advantages and disadvantages of the network model.how it differ from relational model ?
23.Compare BCNF and 3NF