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1. What is database?

A database is a logically coherent collection of data with some inherent meaning, representing some aspect of
real world and which is designed, built and populated with data for a specific purpose.

2. What is DBMS?

It is a collection of programs that enables user to create and maintain a database. In other words it is general purpose software that provides the users with the processes of defining, constructing and manipulating the
database for various applications.

3. What is a Database system?

The database and DBMS software together is called as Database system.

4. What are the advantages of DBMS?

1. Redundancy is controlled.
2. Unauthorised access is restricted.
3. Providing multiple user interfaces.
4. Enforcing integrity constraints.
5. Providing backup and recovery.

5. What are the disadvantage in File Processing System?

1. Data redundancy and inconsistency.
2. Difficult in accessing data.
3. Data isolation.
4. Data integrity.
5. Concurrent access is not possible.
6. Security Problems.

6. Describe the three levels of data abstraction?

The are three levels of abstraction:
1. Physical level: The lowest level of abstraction describes how data are stored.
2. Logical level: The next higher level of abstraction, describes what data are stored in database and what
relationship among those data.
3. View level: The highest level of abstraction describes only part of entire database.

7. Define the "integrity rules"?

There are two Integrity rules.

1. Entity Integrity: States that “Primary key cannot have NULL value”
2. Referential Integrity: States that “Foreign Key can be either a NULL value or should be Primary Key
value of other relation.

8. What is extension and intension?

1. Extension: It is the number of tuples present in a table at any instance. This is time dependent.
2. Intension: It is a constant value that gives the name, structure of table and the constraints laid on it.

9. What is Data Independence?

Data independence means that “the application is independent of the storage structure and access strategy of
data”. In other words, The ability to modify the schema definition in one level should not affect the schema
definition in the next higher level.
Two types of Data Independence:
1. Physical Data Independence: Modification in physical level should not affect the logical level.
2. Logical Data Independence: Modification in logical level should affect the view level.

10. What is a view? How it is related to data independence?

A view may be thought of as a virtual table, that is, a table that does not really exist in its own right but is
instead derived from one or more underlying base table. In other words, there is no stored file that direct
represents the view instead a definition of view is stored in data dictionary.
Growth and restructuring of base tables is not reflected in views. Thus the view can insulate users from the
effects of restructuring and growth in the database. Hence accounts for logical data independence.

11. What is Data Model?

A collection of conceptual tools for describing data, data relationships data semantics and constraints.

12. What is E-R model?

This data model is based on real world that consists of basic objects called entities and of relationship among
these objects. Entities are described in a database by a set of attributes.

13. What is Object Oriented model?

This model is based on collection of objects. An object contains values stored in instance variables with in the
object. An object also contains bodies of code that operate on the object. These bodies of code are called
methods. Objects that contain same types of values and the same methods are grouped together into classes.

14. What is an Entity?

It is a ‘thing’ in the real world with an independent existence.

15. What is an Entity set?

It is a collection of all entities of particular entity type in the database.

15. What is Weak Entity set?

An entity set may not have sufficient attributes to form a primary key, and its primary key compromises of its
partial key and primary key of its parent entity, then it is said to be Weak Entity set.

16. What is an attribute?

It is a particular property, which describes the entity.

17. What is a Relation Schema and a Relation?

A relation Schema denoted by R(A1, A2, …, An) is made up of the relation name R and the list of attributes Ai
that it contains. A relation is defined as a set of tuples. Let r be the relation which contains set tuples (t1, t2, t3,
…, tn). Each tuple is an ordered list of n-values t=(v1,v2, …, vn).

18. What is degree of a Relation?

It is the number of attribute of its relation schema.

19. What is Relationship?

It is an association among two or more entities.

20. What is Relationship set?

The collection (or set) of similar relationships.

21. What is degree of Relationship type?

It is the number of entity type participating.

22. What is DDL (Data Definition Language)?

A data base schema is specifies by a set of definitions expressed by a special language called DDL.

23. What is VDL (View Definition Language)?

It specifies user views and their mappings to the conceptual schema.

24. What is SDL (Storage Definition Language)?

This language is to specify the internal schema. This language may specify the mapping between two schemas.

25. What is Data Storage - Definition Language?

The storage structures and access methods used by database system are specified by a set of definition in a
special type of DDL called data storage-definition language.

26. What is DML (Data Manipulation Language)?

This language that enable user to access or manipulate data as organised by appropriate data model.
1. Procedural DML or Low level: DML requires a user to specify what data are needed and how to get
those data.
2. Non-Procedural DML or High level: DML requires a user to specify what data are needed without
specifying how to get those data.

27. What is Relational Algebra?

It is procedural query language. It consists of a set of operations that take one or two relations as input and
produce a new relation.

28. What is Relational Calculus?

It is an applied predicate calculus specifically tailored for relational databases proposed by E.F. Codd.

29. How does Tuple-oriented relational calculus differ from domain-oriented relational calculus?

1. The tuple-oriented calculus uses a tuple variables i.e., variable whose only permitted values are tuples
of that relation. E.g. QUEL
2. The domain-oriented calculus has domain variables i.e., variables that range over the underlying
domains instead of over relation. E.g. ILL, DEDUCE.

30. What is normalization?

It is a process of analysing the given relation schemas based on their Functional Dependencies (FDs) and
primary key to achieve the properties:

  1. Minimizing redundancy

  2. Minimizing insertion, deletion and update anomalies

31. What is Functional Dependency?

A Functional dependency is denoted by X Y between two sets of attributes X and Y that are subsets of R
specifies a constraint on the possible tuple that can form a relation state r of R. The constraint is for any two
tuples t1 and t2 in r if t1[X] = t2[X] then they have t1[Y] = t2[Y]. This means the value of X component of a
tuple uniquely determines the value of component Y.

32. What is Lossless join property?

It guarantees that the spurious tuple generation does not occur with respect to relation schemas after

33. What is 1 NF (Normal Form)?

The domain of attribute must include only atomic (simple, indivisible) values.

34. What is Fully Functional dependency?

It is based on concept of full functional dependency. A functional dependency X Y is full functional
dependency if removal of any attribute A from X means that the dependency does not hold any more.

35. 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.

36. What is 3NF?

A relation schema R is in 3NF if it is in 2NF and for every FD X A either of the following is true
1. X is a Super-key of R.
2. A is a prime attribute of R.
In other words, if every non prime attribute is non-transitively dependent on primary key.

37. What is BCNF (Boyce-Codd Normal Form)?

A relation schema R is in BCNF if it is in 3NF and satisfies an additional constraint that for every FD X A, X
must be a candidate key.

38. What is 4NF?

A relation schema R is said to be in 4NF if for every Multivalued dependency X Y that holds over R, one of
following is true.
1.) X is subset or equal to (or) XY = R.
2.) X is a super key.

39. What is 5NF?

A Relation schema R is said to be 5NF if for every join dependency {R1, R2, …, Rn} that holds R, one the
following is true

1.) Ri = R for some i.
2.) The join dependency is implied by the set of FD, over R in which the left side is key of R.

40. What is Domain-Key Normal Form?

A relation is said to be in DKNF if all constraints and dependencies that should hold on the the constraint can be
enforced by simply enforcing the domain constraint and key constraint on the relation.

41. What are partial, alternate, artificial, compound and natural key?

1. Partial Key: It is a set of attributes that can uniquely identify weak entities and that are related to same
owner entity. It is sometime called as Discriminator.
2. Alternate Key: All Candidate Keys excluding the Primary Key are known as Alternate Keys.
3. Artificial Key: If no obvious key, either stand alone or compound is available, then the last resort is to
simply create a key, by assigning a unique number to each record or occurrence. Then this is known as
developing an artificial key.
4. Compound Key: If no single data element uniquely identifies occurrences within a construct, then
combining multiple elements to create a unique identifier for the construct is known as creating a
compound key.
5. Natural Key: When one of the data elements stored within a construct is utilized as the primary key,
then it is called the natural key.

42. What is indexing and what are the different kinds of indexing?

Indexing is a technique for determining how quickly specific data can be found.
1. Binary search style indexing
2. B-Tree indexing
3. Inverted list indexing
4. Memory resident table
5. Table indexing

43. What is meant by query optimization?

The phase that identifies an efficient execution plan for evaluating a query that has the least estimated cost is
referred to as query optimization.

44. What is durability in DBMS?

Once the DBMS informs the user that a transaction has successfully completed, its effects should persist even if
the system crashes before all its changes are reflected on disk. This property is called durability.

45. What do you mean by atomicity and aggregation?

1. Atomicity: Either all actions are carried out or none are. Users should not have to worry about the effect
of incomplete transactions. DBMS ensures this by undoing the actions of incomplete transactions.
2. Aggregation: A concept which is used to model a relationship between a collection of entities and
relationships. It is used when we need to express a relationship among relationships.


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46. What are the different phases of transaction?

Different phases are
1.) Analysis phase,
2.) Redo Phase,
3.) Undo phase.

47. What are the different phases of transaction?

Different phases are
1.) Analysis phase,
2.) Redo Phase,
3.) Undo phase.

48. What are the primitive operations common to all record management systems?

Addition, deletion and modification.

49. What are the unary operations in Relational Algebra?


50. Are the resulting relations of PRODUCT and JOIN operation the same?

PRODUCT: Concatenation of every row in one relation with every row in another.
JOIN: Concatenation of rows from one relation and related rows from another.

51. What is database Trigger?

A database trigger is a PL/SQL block that can defined to automatically execute for insert, update, and delete
statements against a table. The trigger can e defined to execute once for the entire statement or once for every
row that is inserted, updated, or deleted. For any one table, there are twelve events for which you can define
database triggers. A database trigger can call database procedures that are also written in PL/SQL.

52. What are cursors give different types of cursors?

PL/SQL uses cursors for all database information accesses statements. The language supports the use two types
of cursors
1.) Implicit
2.) Explicit

53. What are insertion and deletion anomalies?

A deletion anomaly occurs when, by deleting the facts about one entity, we inadvertently delete facts about
another entity; with one deletion, we lose facts about two entities. For example, if we delete the tuple for
Student 001289 from a table, we may lose not only the fact that Student 001289 is in Pierce Hall, but also the
fact that he has $200 left in his security deposit. An insertion anomaly happens when we encounter the
restriction that we cannot insert a fact about one entity until we have an additional fact about another entity. For
example, we want to store the fact that the security deposit for Pierce Hall is $300, but we cannot enter this data
into the Student relation until a student registers for Pierce Hall.

54. You have been given a set of tables with data and asked to create a new database to store them. When you examine the data values in the tables, what are you looking for?

(1) Multivalued dependencies

(2) Functional dependencies,

(3) Candidate keys

(4) Primary keys and

(5) Foreign keys.

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