Defining Nested Memeber functions, Prog to make use of nested member functions. Book- E.Balagurusamy
Thursday, 3 April 2014
Wednesday, 2 April 2014
Short Question Answers
Define DBMS.
What are the different types of
normalization that exists in the database?
How de-normalization is different from
normalization?
What is the type of de-normalization?
How many levels of data abstraction
present?
What do you understand by Data
Independence?
How view is related to data independence?
Why E-R models are used?
What is the purpose of acid properties?
What do you understand by cardinality and
why it is used?
A Database-management system consists of a collection of interrelated data and a set of programs to access those data. The collection of data, usually referred to as the database, contains information about one particular enterprise. The primary goal of a DBMS is to provide an environment that is both convenient and efficient to use in retrieving and storing database information.
What is transaction?
A transaction is a unit of program execution that accesses and possibly updates various data items. A transaction usually results from the execution of a user program written in a high-level data-manipulation language or programming language, and is delimited by statements of the form begin transaction and end transaction. The transaction consists of all operations executed between the begin and end of the transaction. List the properties of transaction.
1. Atomicity
2. Consistency
3. Isolation
4. DurabilityList the possible transaction states.
1. Active
2. Partially committed
3. Aborted
4. Committed
A transaction is a unit of program execution that accesses and possibly updates various data items. A transaction usually results from the execution of a user program written in a high-level data-manipulation language or programming language, and is delimited by statements of the form begin transaction and end transaction. The transaction consists of all operations executed between the begin and end of the transaction. List the properties of transaction.
1. Atomicity
2. Consistency
3. Isolation
4. DurabilityList the possible transaction states.
1. Active
2. Partially committed
3. Aborted
4. Committed
Define RAID.It is collectively called redundant arrays of inexpensive disk, have been proposed to address the performance and reliability issues. Raids are used for their higher reliability and higher data transfer rate. RAID stands for independent, instead of inexpensive.
Define Functional Dependency.
Functional dependencies are constraints on the set of legal relations. They allow us to express facts about the enterprise that we are modeling with our database. Syntax: A -> B e.g.) account no -> balance for account table. List the pitfalls in Relational Database Design.
1. Repetition of information
2. Inability to represent certain information
25. Define normalization.
By decomposition technique we can avoid the Pitfalls in Relational Database Design. This process is termed as normalization. List the properties of decomposition.
1. Lossless join
2. Dependency Preservation
3. No repetition of informationDefine First Normal Form.
If the Relation R contains only the atomic fields then that Relation R is in first normal form. E.g.) R = (account no, balance) – first normal form. Define SecondNormal Form.
A relation schema R is in 2 NF with respect to a set F of FD’s if for all FD’s of the form A -> B, where A is contained in R and B is contained in R, and A is a superkey for schema R. Define BCNF.
A relation schema R is in BCNF with respect to a set F of FD’s if for all FD’s of the form A -> B, where A is contained in R and B is contained in R, at least one of the following holds: 1. A -> B is a trivial FD
2. A is a superkey for schema R.
Functional dependencies are constraints on the set of legal relations. They allow us to express facts about the enterprise that we are modeling with our database. Syntax: A -> B e.g.) account no -> balance for account table. List the pitfalls in Relational Database Design.
1. Repetition of information
2. Inability to represent certain information
25. Define normalization.
By decomposition technique we can avoid the Pitfalls in Relational Database Design. This process is termed as normalization. List the properties of decomposition.
1. Lossless join
2. Dependency Preservation
3. No repetition of informationDefine First Normal Form.
If the Relation R contains only the atomic fields then that Relation R is in first normal form. E.g.) R = (account no, balance) – first normal form. Define Second
A relation schema R is in 2 NF with respect to a set F of FD’s if for all FD’s of the form A -> B, where A is contained in R and B is contained in R, and A is a superkey for schema R. Define BCNF.
A relation schema R is in BCNF with respect to a set F of FD’s if for all FD’s of the form A -> B, where A is contained in R and B is contained in R, at least one of the following holds: 1. A -> B is a trivial FD
2. A is a superkey for schema R.
Define 3 Normal Form.
A relation schema R is in 3 NF with respect to a set F of FD’s if for all FD’s of the form A -> B, where A is contained in R and B is contained in R, at least one of the following holds:
1. A -> B is a trivial FD
2. A is a superkey for schema R.
3. Each attribute in B – A is contained in a candidate key for R.Define Nested Sub queries.
SQL provides a mechanism for the nesting of sub queries. A sub query is a select-from-where expression that is nested within another query. A common use of sub queries is to perform tests for set membership, set comparisons, and set cardinality. Define Embedded SQL.
The SQL standard defines embeddings of SQL in a variety of programming languages, such as Pascal, PL/I, Fortran, C, and COBOL. A language in which SQL queries are embedded is referred to as a host language, and the SQL structures permitted in the host language constitute embedded SQL. Define Integrity Constraints.
Integrity constraints provide a means of ensuring that changes made to the database by authorized users do not result in a loss of data consistency. Thus Integrity Constraints guard against accidental damage to the database. The constraints were in the following forms: Key declarations, and Form of a relationship. Define Referential Integrity.
Often, we wish to ensure that a value that appears in one relation for a given set of attributes also appears for a certain set of attributes in another relation. This condition is called referential integrity.
A relation schema R is in 3 NF with respect to a set F of FD’s if for all FD’s of the form A -> B, where A is contained in R and B is contained in R, at least one of the following holds:
1. A -> B is a trivial FD
2. A is a superkey for schema R.
3. Each attribute in B – A is contained in a candidate key for R.Define Nested Sub queries.
SQL provides a mechanism for the nesting of sub queries. A sub query is a select-from-where expression that is nested within another query. A common use of sub queries is to perform tests for set membership, set comparisons, and set cardinality. Define Embedded SQL.
The SQL standard defines embeddings of SQL in a variety of programming languages, such as Pascal, PL/I, Fortran, C, and COBOL. A language in which SQL queries are embedded is referred to as a host language, and the SQL structures permitted in the host language constitute embedded SQL. Define Integrity Constraints.
Integrity constraints provide a means of ensuring that changes made to the database by authorized users do not result in a loss of data consistency. Thus Integrity Constraints guard against accidental damage to the database. The constraints were in the following forms: Key declarations, and Form of a relationship. Define Referential Integrity.
Often, we wish to ensure that a value that appears in one relation for a given set of attributes also appears for a certain set of attributes in another relation. This condition is called referential integrity.
Define Fourth Normal Form.
A relation schema R is in 4NF with respect to a set F of FD’s if for all FD’s of the form A ->> B (Multi valued Dependency), where A is contained in R and B is contained in R, at least one of the following holds:
1. A ->> B is a trivial MD
2. A is a superkey for schema R.
3. Define 5NF or Join Dependencies.
Let R be a relation schema and R1, R2, …, Rn be a decomposition of R. The join dependency *(R1, R2, …Rn) is used to restrict the set of legal relations to those for which R1,R2,…Rn is a lossless-join decomposition of R. Formally, if R= R1 U R2U …U Rn, we say that a relation r® satisfies the join dependency *(R1, R2, …Rn) if R = A join dependency is trivial if one of the Ri is R itself.
A relation schema R is in 4NF with respect to a set F of FD’s if for all FD’s of the form A ->> B (Multi valued Dependency), where A is contained in R and B is contained in R, at least one of the following holds:
1. A ->> B is a trivial MD
2. A is a superkey for schema R.
3. Define 5NF or Join Dependencies.
Let R be a relation schema and R1, R2, …, Rn be a decomposition of R. The join dependency *(R1, R2, …Rn) is used to restrict the set of legal relations to those for which R1,R2,…Rn is a lossless-join decomposition of R. Formally, if R= R1 U R2U …U Rn, we say that a relation r® satisfies the join dependency *(R1, R2, …Rn) if R = A join dependency is trivial if one of the Ri is R itself.
what is data definition language?
data scheme is specified by a set of definitions which are expressed b a special
language called a DDL.
what is a data directory or data dictionary?
the result of compilation of DDL statements is a set of tables which are stored
in a special file called data dictionary or data directory.
a data directory is a file that contains metadata i.e data about data.this file
is consulted before actual is read or modified in the database system.
data scheme is specified by a set of definitions which are expressed b a special
language called a DDL.
what is a data directory or data dictionary?
the result of compilation of DDL statements is a set of tables which are stored
in a special file called data dictionary or data directory.
a data directory is a file that contains metadata i.e data about data.this file
is consulted before actual is read or modified in the database system.
Define
Query processing?
Query processing refers to the range of activities involved in extracting data form a database. These activities include translation of queries expressed in high-level database language into expression that can be implemented at the physical level of the file system.
Query processing refers to the range of activities involved in extracting data form a database. These activities include translation of queries expressed in high-level database language into expression that can be implemented at the physical level of the file system.
Why a
database is called as relational database model?
A database model represents the
relationship between one or more databases. The relationship is known as the
relational database model. It is an extension of the normal databases without
relations. It provides flexibility and allows one database to be in relation
with another database. It can access the data from many databases at one time
over the network.
What are
entities and attributes referring to?
Table consists of some properties
that are known as attributes. These consist of the representation of entity in
the table. They are represented by columns in the table. Entity is referred to
the store data about any particular thing. It is the smallest unit inside the
table.
What do you understand by database
Normalization?
Normalization is very
essential part of relational model. It consists of set of procedures that
eliminates the domains that are non-atomic and redundancy of data that prevents
data manipulation and loss of data integrity. Normal forms are the common form
of normalization. It helps in reducing redundancy to increase the information
overall. It has some disadvantages as it increases complexity and have some
overhead of processing.
What are the different types of
normalization that exists in the database?
There are 9
normalizations that are used inside the database. These are as follows:
1. First normal form: in this table represents a relation that has no repeating groups
2. Second normal form: non- prime attributes are not functional dependent on subset of any candidate key.
3. Third normal form: in a table every non- prime attribute is non-transitively dependent on every candidate key
4. Elementary key normal form: superkey dependency or elementary key dependency effects the functional dependency in a table
5. Boyce codd normal form: “every non-trivial functional dependency in the table is dependent on superkey”.
6. Fourth normal form: “Every non-trivial multivalued dependency in the table is a dependent on a superkey”.
7. Fifth normal form (5NF): “Every non-trivial join dependency in the table is implied by the superkeys of the table”.
8. Domain/key normal form (DKNF): “Every constraint on the table is a logical consequence of the table's domain constraints and key constraints”
9. Sixth normal form (6NF): “Table features no non-trivial join dependencies at all”.
1. First normal form: in this table represents a relation that has no repeating groups
2. Second normal form: non- prime attributes are not functional dependent on subset of any candidate key.
3. Third normal form: in a table every non- prime attribute is non-transitively dependent on every candidate key
4. Elementary key normal form: superkey dependency or elementary key dependency effects the functional dependency in a table
5. Boyce codd normal form: “every non-trivial functional dependency in the table is dependent on superkey”.
6. Fourth normal form: “Every non-trivial multivalued dependency in the table is a dependent on a superkey”.
7. Fifth normal form (5NF): “Every non-trivial join dependency in the table is implied by the superkeys of the table”.
8. Domain/key normal form (DKNF): “Every constraint on the table is a logical consequence of the table's domain constraints and key constraints”
9. Sixth normal form (6NF): “Table features no non-trivial join dependencies at all”.
How de-normalization is different from
normalization?
Analytical processing
databases are not very normalized. The operations which are used are read most
databases. It is used to extract the data that are ancient and accumulated over
long period of time. For this purpose de-normalization occurs that provide
smart business applications. Dimensional tables in star schema are good example
of de-normalized data. The de-normalized form must be controlled while
extracting, transforming, loading and processing. There should be constraint
that user should not be allowed to view the state till it is consistent. It is
used to increase the performance on many systems without RDBMS platform.
What is the type of de-normalization?
Non-first normal form
(NFA) – it describes the definition of the database design which is different
from the first normal form. It keeps the values in structured and specialized
types with their own domain specific languages. The query language used in this
is extended to incorporate more support for relational domain values by adding
more operators.
How many levels of data abstraction
present?
There are three
levels of data abstraction that is present in database model and these are as
follows:
1. physical level: it is the lowest level that describes how data is stored inside the database.
2. logical level: it is the next higher level in the hierarchy that provides the abstraction. It describes what data are stored and the relationship between them.
3. view level : it is the highest level in hierarch that describes part of the entire database. It allows user to view the database and do the query.
1. physical level: it is the lowest level that describes how data is stored inside the database.
2. logical level: it is the next higher level in the hierarchy that provides the abstraction. It describes what data are stored and the relationship between them.
3. view level : it is the highest level in hierarch that describes part of the entire database. It allows user to view the database and do the query.
What do you understand by Data
Independence?
Data independence
tells about the independence of the data inside the application. It usually
deals with the storage structure and represents the ability to modify the
schema definition. It doesn’t affect the schema definition which is being
written on the higher level. There are two types of data independence:
1. Physical data independence: it allow the modification to be done in physical level and doesn’t affect the logical level.
2. Logical data independence: it allow the modification to be done at logical level and affects the view level. <p>NOTE: Logical Data Independence is more difficult to achieve. </p>
1. Physical data independence: it allow the modification to be done in physical level and doesn’t affect the logical level.
2. Logical data independence: it allow the modification to be done at logical level and affects the view level. <p>NOTE: Logical Data Independence is more difficult to achieve. </p>
How view is related to data independence?
View is a virtual
table that doesn’t really exist, but it remains present so that user can view
their data. It is derived from the base table. The view is stored in the data
dictionary and represents the file directly. The base table updation or
reconstruction is not being reflected in views. It is related to the logical
data independence as it is at the logical level and not at the physical level.
Why E-R models are used?
E-R model stands for
entity-relationship model and it is used to represent a model with their
relationships. This is an object oriented approach and it is based on real
world that consists of objects which are called entities and relationship
between them. Entities are further used inside the database in the form of
attributes.
What is the purpose of acid properties?
ACID stands for
Atomicity, Consistency, Isolation and durability and it plays an important role
in the database. These properties allow the database to be more convenient to
access and use. This allows data to be shared more safely in between the
tables. If these properties are not being implemented then the data will become
inconsistent and inaccurate. It helps in maintaining the accuracy of the data
in the database.
What do you understand by cardinality and
why it is used?
Cardinality is
important and used to arrange the data inside the database. It is related to
the design part and need to be properly used in database. It is used in E-R
diagrams and used to show the relationship between entities/tables. It has many
forms like the basic is one to one, which associate one entity with another.
Second is one to many: which relates one entity with many entities in a table.
Third is many to many M: N that allows many entities to be related to many more.
Last is many to one that allows the many entities to be associated with one entity.
Second is one to many: which relates one entity with many entities in a table.
Third is many to many M: N that allows many entities to be related to many more.
Last is many to one that allows the many entities to be associated with one entity.
What is the difference between DBMS and RDBMS?
• DBMS is persistent and accessible when the data is created or exists, but RDBMS tells about the relation between the table and other tables.
• RDBS supports a tabular structure for data and relationship between them in
the system whereas DBMS supports only the tabular structure.
• DBMS provide uniform methods for application that has to be independently accessed, but RDBMS doesn’t provide methods like DBMS but provide relationship which link one entity with another.
• DBMS provide uniform methods for application that has to be independently accessed, but RDBMS doesn’t provide methods like DBMS but provide relationship which link one entity with another.
What do you understand by relation in relational database model?
Relation in the relational database model is defined as the set of tuples that have the same attributes. Tuple represents an object and also the information that the object contains. Objects are basically instances of classes and used to hold the larger picture. Relation is described as a table and is organized in rows and columns. The data referenced by the relation come in the same domain and have the same constraints as well. Relations in the relational database model can be modified using the commands like insert, delete etc.
Why domain is of high importance?
Domain describes possible values grouped together that can be given for an attribute. It is considered the same way as a constraint on the value of attribute. A domain can be attached to an attribute but only if the attribute is an element of specified set. For example: XYZ doesn’t fulfill the domain constraint but the integer value as 899 fulfills the criteria of domain constraint. Hence, domain is of high importance.
What is the difference between base and derived relation?
Relational database means the relationship between different databases. In relational database user can store and access all the data through the tables which are related to each other. Relationship between the store data is called base relations and implementation of it is called as tables. Whereas, relations which don’t store the data, but can be found out by applying relational operations on other relations are called as derived relations. When these are implemented they are termed as views or queries.
Derived relations are more useful then base relation, as they can have more information from many relations, but they act as a single relation.
Derived relations are more useful then base relation, as they can have more information from many relations, but they act as a single relation.
What are constraints in database?
Constraints are kind of restrictions that are applied to the database or on the domain of an attribute. For example an integer attribute is restricted from 1-10 and not more than that. They provide the way to implement the business logic and the rules in database. In database it can be implemented in the form of check constraints that checks for the rules that haven’t been followed by the programmer. Constraint also used to restrict the data that can be stored in the relations. Domain constraint can be applied to check the domain functionality and keep it safe..
Topic (FCPIT)
Declaring & Defining Classes, Defining member functions of class. Book - OOPS By E. Balagurusamy, pg-96-104
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