september / october-2009[12bca38,12bca37,12bca40]€¦ · web viewa transaction is a collection...

SEPTEMBER / OCTOBER-2009 [12BCA37,12BCA38,12BCA40]

Sr.no Que-Ans Marks

Q-1 Answer the following question. 12.

1 What is data manager? List the responsibilities of the database

manager.

Ans: Data manager is the central software components of the DBMS. Responsibilities of data manager are Responsible for interfacing with file system. Enforcing constrain to maintain the consistency and integrity of

data. Maintaining security Convert operations in users query.

2 Define the team :

A.Database schema :

B.Database:

Ans: A. Database schema :

In a relational database the schema define the table the

field in each table and the relationship between fields and

table.

Schema has a two types

1. Physical schema.

2. Logical schema.

B. Database:

A systematic type of argument of related information is

called a database.

3. Differentiate between physical and logical data independence.

Ans: Physical Independence: It indicates that the physical storage structure of storage or devices used for storing could be changed without necessity a change in conceptual view or any of the external views. Logical independence: It indicates that the conceptual schema can

be changed without affecting the existing external schemas.4. Explain association with example.

Ans: A relationship is an association among several entities. For Eg.customer and loan are two entities we can define a relation that

associated customer Harish with loan L-1.5. Explain query processor.

Ans: Function of query processor is to break down DML statement into instruction the storage manager understands.

Component of processor are DDL interpreter query that the which interprets DDL statement.

DML compiler which translate DML statement in a query language into evaluation plan.


Query evaluation engine which executes low level instruction generated by DML compiler.

6. State the difference between functional and multivalued

dependencies.

Ans: Functional dependencies :Given two set of attributes X&Y.Y is said to be functionally dependant on X it a given for each attributes in X uniquely determines the values of the attributes in Y.X is called the determinant of the functional

Dependency (fd) and fd is denotes by X>Y. Multivalued dependencies. : Given a relation schema R, let X&Y be subset of attributes of R and Y need not be distinct. Then multivalued dependencies x>y hold in a relation R define R if

given two tuples t1 and t2 in R with t1(X)=t2(X) R contain two tuples t3 and t4 with the following characteristics:

T1, T2, T3 and T4 the same values X. T1(X)=t2(X)=t3(X)=t4(X) The Y values of t1 and t3 are the same The Y values of t2 and t4 the

same T1(Y)=t2(Y)=t3(Y)=t4(Y)

Q2. Answer in brief.

a. Write a note on database system user.

Ans: Application programmers – interact with system through DML callsSophisticated users – form requests in a database query language Specialized users – write specialized database applications that do not fit into the traditional data processing framework.

Naïve users – invoke one of the permanent application programs that have been written previously E.g. people accessing database over the web, bank tellers, clerical

staff Users are differentiated by the way they expect to interact with the

system A transaction is a collection of operations that performs a single

logical function in a database application. Transaction-management component ensures that the database

remains in a consistent (correct) state despite system failures (e.g., power failures and operating system crashes) and transaction failures.

Concurrency-control manager controls the interaction among the concurrent transactions, to ensure the consistency of the database.

08.


(or)

a. Discuss type of record-base logical model. Differentiate them with each other.

Ans: 1. Record-based logical models: Also describe data at the conceptual and view levels. Unlike object-oriented models, are used to Specify overall logical

structure of the database, and provide a higher-level description of the implementation.

Named so because the database is structured in xed-format records of several types.

Each record type de nes a xed number of elds, or attributes. Each end is usually of a xed length (this simpli es the

implementation). Record-based models do not include a mechanism for direct

representation of code in the database. Separate languages associated with the model are used to express

database queries and updates. The three most widely-accepted models are the relational, network,

08.


and hierarchical.

Name street city number

Lowery Maple Queens 900

Shiver North Bronx 556

Shiver North Bronx 647

Hodges Sidehill Brooklyn 801

Hodges Sidehill Brooklyn 647

This course will concentrate on the relational model. The network and hierarchical models are covered in appendices in the

text.

The Relational Model: Data and relationships are represented by a collection of tables. Each table has a number of columns with unique names, e.g. customer, account Figure 1.3 shows a sample relational database.Figure 1.3: A sample relational database.

Figure 1.4: A sample network database

The Network Model: Data are represented by collections of records. Relationships among data are represented by links. Organization is that of an arbitrary graph. Figure 1.4 shows a sample network database that is the equivalent of

the relational database of Figure 1.3.The Hierarchical Model Similar to the network model. Organization of the records is as a collection of trees, rather than

arbitrary graphs. Figure 1.5 shows a sample hierarchical database that is the equivalent

of the relational database of Figure 1.3.Figure 1.5: A sample hierarchical database


The relational model does not use pointers or links, but relates records by the values they contain. This allows a formal mathematical foundation to be defined.

b. Define relationship. Explain types of relationship with

example.

Ans: A relationship is an association among several entities.For example a depositor relation ship assosiated customer with each account that she/he has.

The number of entities set that partcipate in a relationship set is also the relationship set is of degree 3.

Various types of relationship are Binary relationship ternary relationship

Binary relationship: The relationship set borrow and loan branch provide an example of a

binary relationship set that is one that involes two entities set.

As example considers the entity set employee, branch and job.

Examples of job could include manager teller auditor and so on job

05.


entities may have the attributes title and level.

The relationship set works on among employee branch and job is an example of a ternary relationship.

(or)

b. Compare BCNF and 3RD NF.

Ans: BCNF 3RD NF1 In BCNF for every x>y,

Y is subset of X X is super key.

In 3NF for every X>Y, Y is subset of X. X is not super key. Y is not subset of key.

2 BCNF don’t have any redundancy.

3NF has some redundancy

3 BCNF is not dependency preserving.

3NF is dependency preserving

4 The relation in #NF is now decomposed to bring it to BCNF FD of original tables are FD:FD1:stu#,sub>teacherFD:FD2: stu#,sub>scoreFD:FD3: stu#,sub>subExample:Teac Sub

Teacher SubjectRaturi Chem.Siya EnglishJiya HistoryRitika CS

FD 1: teacher >subjectStu# Sub1H123 Chem.1H124 English1H234 History1H254 CS1H235 Chem.

FD11:stu#,sub>scoreAs per FDs inferd from teach_sub&stu#_score tableside are fd1:teacher>subjectFd2:stu#,sub,sub>scoreOriginal tables have 2 FDs and also not same as original table.Thus in BCNF dependency not preserved.

Example:Stud# Sub teache

rScore

1H123

chem Raturi 4

1H124

English

Siya 4

1H234

History

Jiya 3

1H254

CS Ritika 3

1H235

chem Roma 2

FD:FD1:stu#,sub>teacherFD:FD2: stu#,sub>scoreFD:FD3: teacher>subKey:stu#sub

In FD1,fd2,fd3 there is no partial dependency so relation is in 2NF.

In fd1 stu#,sub is key in fd2 Stu#, sub is key and in fd3 sub at dependant side is prime attribute and as per 3NF either determinant should be key or dependant is prime attribute so this relation is in 3NF.

3.but still having data redundancy

05.

Q-3 Write a short note on any three with an example. 21.


1. Explain Generalization and Specialization.

Ans: Consider extending the entity set account by classifying accounts as being either saving-account or chequing-account.

Figure : Generalization

Each of these is described by the attributes of account plus additional attributes. (savings has interest-rate and chequing has overdraft-amount.)

We can express the similarities between the entity sets by generalization.

This is the process of forming containment relationships between a higher-level entity set and one or more lower-level entity sets.

In E-R diagrams, generalization is shown by a triangle, as shown in Figure. Generalization hides dierences and emphasizes similarities. Distinction made through attribute inheritance. Attributes of higher-level entity are inherited by lower-level

entities. Two methods for conversion to a table form:

_ Create a table for the high-level entity, plus tables for the lower-level entities containing also their specific attributes._ Create only tables for the lower-level entities.

Specialization Top-down design process; we designate sub groupings within an

entity set that are distinctive from other entities in the set. These sub groupings become lower-level entity sets that have

attributes or participate in relationships that do not apply to the higher-level entity set.

Depicted by a triangle component libelled ISA (E.g. customer “is a” person).

Attribute inheritance A lower-level entity set inherits all the attributes and relationship participation of the higher-level entity set to which it is linked.


2. Date manipulation statement in sql.Ans: Data Manipulation(DML) :

retrieval of information from the database insertion of new information into the database deletion of information in the database modication of information in the database A DML is a language which enables users to access and

manipulate data. The goal is to provide ecient human interaction with the system. There are two types of DML

Procedural: The user species what data is needed and how to get it Nonprocedural: The user only species what data is needed

Easier for user May not generate code as ecient as that produced by

procedural languages A query language is a portion of a DML involving

information retrieval only. The terms DML and query language are often used synonymously.

Data Manipulation Language (DML): DML statements are used for managing data within schema objects. Some example:

Command DescriptionSELECT: Retrieve data from the a databaseINSERT: Insert data into a tableUPDATE: Update existing data within a tableDELETE: Deletes all records from a table, the space

for the records remainMERGE: UPSERTE operation (insert or update)CALL: Call a PL/SQL or java subprogramEXPLAI PLAN:

Explain access path or data

LOCK TABLE: Control concurrency


3. Integrity constraint.

Ans: Integrity constrain are used to ensure accuracy and consistency

of data in a relational database.

Data integrity is handled in a relational database through the

concept or referential integrity.

There are many type of integrity constrain.

Entity integrity.

Referential integrity.

Domain integrity.

Entity integrity :-

Entity integrity is an integrity rule which states that every

table must have a primary key and that the column or chosen to be

the primary key should be unique and not null.

If each value of a primary key must be unique no duplicate row

can logically appear in a table.

The not NULL characteristic of a primary key ensures that a

value can be use to identify all rows in a table.

Within relational database using SQL, entity integrity is

enforced by adding a primary key cause to a schema definition.

Referential integrity:

There are cases where we wish to ensure that a value that

appears in one relation for a given set of attribute also appears for

a certain set of attributes in another relation this is called

referential integrity.

Database modification can cause violation of referential

integrity.

When a referential integrity constrain is violated the normal

procedure is to reject the action that caused violation.

Example:

Emp(eid,ename,add,contect_no,);

Dept(dptid,dptname);

Emp_dept(empid,dptid);

In table it can be enforced using following example.

CREATE TABLE EMP

(


EID NUMBER PRIMARY KEY,

ENAME TEXT,

ADD TEXT,

CONTACTECT_NO NUMBER

);

Domain integrity:

A domain defines the possible values of an attribute.

Domain integrity rules govern these values.

In a database system the domain integrity is define by,

The data type and the length

The NULL value acceptance

The allows able values, through techniques like constrain

or rules

The default value.

4. Mapping cardinalities.Ans:

Express the number of entities to which another entity can be associated via a relationship set.

Most useful in describing binary relationship sets.

For a binary relationship set the mapping cardinality must be one of the following types:

1.One to one2.One to many3.Many to one4.Many to many

Explain in brief

1. One to One


One to one One to many

Note: Some elements in A and B may not be mapped to any

elements in the other set

Many to one Many to many

Note: Some elements in A and B may not be mapped to any

elements in the other set

Mapping Cardinalities affect ER Design

Can make access-date an attribute of account, instead of a relationship attribute, if each account can have only one customer

I.e., the relationship from account to customer is many to one, or equivalently, customer to account is one to many .


E-R Diagrams

Rectangles represent entity sets.Diamonds represent relationship sets.Lines link attributes to entity sets and entity sets to relationship sets.Ellipses represent attributesDouble ellipses represent multivalued attributes.

Dashed ellipses denote derived attributes.Underline indicates primary key attributes (will study later)

E-R Diagram With Composite, Multivalued, and Derived Attributes


Relationship Sets with Attributes

Roles:

Entity sets of a relationship need not be distinct

The labels “manager” and “worker” are called roles; they specify how employee entities interact via the works-for relationship set.

Roles are indicated in E-R diagrams by labeling the lines that connect diamonds to rectangles.

Role labels are optional, and are used to clarify semantics of the relationship


Cardinality Constraints

We express cardinality constraints by drawing either a directed line (®), signifying “one,” or an undirected line (—), signifying “many,” between the relationship set and the entity set.

E.g.: One-to-one relationship:

A customer is associated with at most one loan via the relationship borrower

A loan is associated with at most one customer via borrower

One-To-Many Relationship

In the one-to-many relationship a loan is associated with at most one customer via borrower, a customer is associated with several (including 0) loans via borrower


Many-To-One Relationships

In a many-to-one relationship a loan is associated with several (including 0) customers via borrower, a customer is associated with at most one loan via borrower

Many-To-Many Relationship

A customer is associated with several (possibly 0) loans via borrower

A loan is associated with several (possibly 0) customers via borrower

Q-4 Answer the following : 12.

A. Describe the need of normalization and steps to achieve BCNF.

Ans: Definition :

Normalization is the process to filtering database which is to

reduce a normalization and redundancies data.


Normalization is the process of efficiently organising data in

data base.

Goal :

Eliminate redundant data.

Ensuring redundant data is logically staror.

Purpose:

Normalization is the technique for producing a set of relation

with describes properties, given the data requirement of an

enterprise.

The process of normalization is a formal method that identifies

relation base on their primary & candidate key and the

functional dependencies among their attribute.

Need of normalization: Database normalization is the process of organizing the fields

and tables of a relational database to minimize redundancy and dependency.

Normalization usually involves dividing large tables into smaller (and less redundant) tables and defining relationships between them.

A database table looks like a spreadsheet. One item of data, such as a first name, a last name, a phone number,

or a street address, appears in each box, or cell, at each intersection of a row and column.

When you normalize a database you have four goals: Arranging data into logical groupings such that each group

describes a small part of the whole Minimizing the amount of duplicate data stored in a database; Organizing the data such that, when you modify it, you make

the change in only one place Building a database in which you can access and manipulate

the data quickly and efficiently without compromising the integrity of the data in storage.

Data normalization helps you design new databases to meet these goals or to test databases to see whether they meet the goals.

Sometimes database designers refer to these goals in terms such as data integrity, referential integrity, or keyed data access.

Normalization is a process followed for eliminating redundant data and establishes a meaningful relationship among tables based on rules and regulations in order to maintain integrity of data.

Normalization is done for maintaining storage space and also for performance tuning.

1st Normal form :

Rule 1: Eliminate Repeating Groups. Make a separate table for each set of related attributes, and give each table a primary key.


First NF is a relation in which the intersection of each row and

column contain one value.

There are two approaches to removing repeating group for

unnormalization table.

Remove the repeating group by entering appropriate data in

the empty column of row contains the repeating data.

Remove repeating group by placing the repeating data

along with a copy of the original key attribute in a

shaparate relation a primary key is identify for the new

relation.

2nd Normal Form :

Rule 2: Eliminate Redundant Data, if an attribute depends on only part of a multi-valued key, remove it to a separate table.

Second NF is a relation that is in first normal form and every

non-primary key attribute is fully functionally dependent on

the primary key.

Second NF is removing partial dependencies if a partial

dependency exists; we remove the function dependency

attributes form the form the relation by placing them in a new

relation among with a copy of their determinant.

3rd normal form :Rule 3: Eliminate columns not dependent on key. If attributes do not contribute to a description of the key, remove them to a separate table.

A relation that is in first n & second normal form and in which

no none primary key attribute is transitively dependent on the

primary key.

Third nf is remove transitive dependency by placing the

attribute in a new relation among with a copy of the

determinant.

BCNF :Rule 4: Isolate independent multiple relationships. No table may contain two or more 1:N (one-to-many) or N:M (many-to-many) relationships that are not directly related.

Bocyce code normal from.

A relationship in bcnf, if n only if every determine is a


candidate key.

The difference between 3 rd nf and bcnf is that for a functional

dependency a → b 3 rd nf allow this dependency in a relation b

is a primary key attribute in a attribute and a is not a candidate

key.

Where bcnf instance that for this dependency to remain in to

relation a must be candidate key.

B. Explain the concept of keys and their significance.

Ans: Key :

Key is a minimal set of attribute.

A key is an entity set such that number of two entities agrees

on all attribute.

A key is a data item of field which computer using to identify

to records database system which is refer two as keys.

A key is a single attribute or combination of attribute that is

use to identify one or more instance of the set.

There are eight (8) types of keys.

Primary key.


Foreign key/reference key.

Super key.

Candidate key.

Composite key.

Alternate key.

Simple key.

Secondary key.

1.primary key :-

Primary key is a uniquely identification of column is in table.

Primary key has a tow rules given as bellow.

Primary key is a unique.

Primary key is not null.

A primary key is a field that uniquely identifies each record in the database.

When you declare primary key in your table then that table is

called parent table/prime table/main table.

If you can put key in a table then you see the little symbol of

key that particular field’s right side.

Example:

CUSTOMERS

CustomerNo FirstName LastName1 Sally Thompson2 Sally Henderson3 Harry Henderson4 Sandra Wellington

For example, in the table above, Customer No is the primary key.The values placed in primary key columns must be unique for each row: no duplicates can be tolerated. In addition, nulls are not allowed in primary key columns.E.g. of Primary Key - Database designer can use one of the Candidate Key as a Primary Key. In this case we have “Code” and “Name, Address” as Candidate Key, we will consider “Code” Key as a Primary Key as the other key is the combination of more than one attribute.

2. Foreign key/reference key:-

Foreign key/reference key is a relation of two or more table in

which you can take primary key field to another.

Table that referential integrity is created.

When you declare primary key in your table then that table is

called parent table/prime table/main table.


When that primary key is reference in another that which is

called foreign key/reference table/child table/detail table.

If the data is exit in master table then n only then we can use in

child table

Example :-

Table 1:

Field 1 Field 2 Field 3

Reference way

Table 2:Field a Field b Field 1

See above example field 1 has a primary key in table 1 and that

field is again use in table 2 as a references is called a foreign

key/reference key

3. Super key :-

Super key is a set of each field of given table or subset of any

field of that given table.

In shrot,there is primary key in a simple table but when we are

describe that table then their described(subset) table have not a

primary key is called super key.

Example :-

My_emp{empid,ename,salary,doj,design,address};

Here, there is a give one table my_emp, and empid has a primary

key. Now we can describe the table given as below.

Field1{ename,salary,doj,address};

Field2{empid,ename};

Field3{salary, design};

When we are describe the simple table just like

field1,field2,field3 then which described(subset) table has a

primary key it’s not a super key or super table

Here, there are field1 & field3 have not primary key then it is a

super key or super table and field2 have a primary key then it

Primary key


is not a super key or super table.

4.candidate key :-

Candidate key can be define as minimal super key in other

word in attribute a combination of attribute that identify that

record, uniquely but non of is proper subset can identify record

uniquely.

Candidate key has at least one primary key of described

(subset) table.

Candidate key is also super key but super key is not

candidate key.

Example :-

My_emp(empid,ename,salary,doj,design);

Here, there is a give one table my_emp, and empid has a primary

key. Now we can describe the table given as below.

Field1{empid,ename,salary,doj,address};

Field2{ename,salary};

Field3{empid,salary,design};

When we are describe the simple table just like

field1,field2,field3 then which described(subset) table have a

primary key is called candidate key or candidate table

Here, there are field1 & field3 have primary key then it is a

candidate key or candidate table and field2 have not primary

key then it is not a candidate key or candidate table.

Here all table is also know as super key or super table

5.composite key :-

Composite key is a set of two primary key in one table.

Here, you are confused that how it is possible because one

table have an only one primary key then how it is possible? It

confiscation’s answer is given as bellow through examples &

some brief information.

First a fall we can create two tables when the in a table have at

least one primary key and we can meagre that table in third

table as a reference key and that table is define as a composite

key or composite table.


Example :-

Table 1:

Student(sid,sname,city,achievement,contactno);

Table 2:

Course(cid,cname);

Here, there are two tables and is have a primary key to field sid

and cid.

Now we are describing that table and create third table as

stu_course.

Table 3:

Stu_course(sid,cid);

See, here table 3 has a tow primary key before we can describe

that two tables as a stu_course and see table 1 have a primary

key as a sid and table 2 have a primary key as cid and when we

are describe that as a table 3 stu_course sid & cid is a primary

key as a reference key it is called a composite key.

6.alternative key :-

Alternative key can be any of the candidate key accepts for the

primary key.

Alternative key is a combination of that attributes of table have

a no composite key.

In short it is just like a candidate key but it is not candidate

key or super key.

Example :-

Table 1:

Student(sid,sname,city,achievement,contactno);

Table 2:

Course(cid,cname);

Here, there are two tables and is have a primary key field sid

and cid and other field are none selected in key that all are

define as alternative key.

Now we are describing that table and create third table as

stu_course.

Table 3:

Stu_course(sid,cid);

See, here table 3 has a tow primary key before we can describe


that two tables as a stu_course and see table 1 have a primary

key as a sid and table 2 have a primary key as cid and when we

are describe that as a table 3 stu_course sid & cid is a primary

key as a reference key it is called a composite key.

Table 4:

Stu_cource1(sname,city,achiement,contactno,cname);

See, here there are not primary key in a table 4 it is called

alternative key or alternative table.

7.secondary key :-

The attribute that are not event the super key but can be still

use for identification of record not (unique) are know as

secondary key or secondary table.

In short table have a no primary key.

Their records are not uniquely or randomly.

Secondary key is working as an alternate of primary key.

Means secondary key is null.

Secondary key is not unique.

C. Explain the concept of database management system.

Ans DBMS: database management system.

Database: a systematic type of argument of related

information is called a database.

DBMS: Database management system is collection of

interrelated data and a set of program to access those data.

It is a collection of inter related data.

It is set of program to access the data

DBMS is a contain of information about a particular enterprise.

DBMS provide an environment that is both convenient and

efficient to use.

Goal of DBMS: DBMS is providing a way to store and relative

database information that is both convenient and efficient.

Database system application:

Banking.

Airlines.

Universities/schools

Credit card transitions.

Telecommunication.


Finance.

Sales.

On-line retails.

Manufacturing.

Human resource.

Purpose of database system(drawback of file processing

system):

Data redundancy and inconsistency.

Difficulty in accessing data.

Data isolation.

Integrity problem.

Atomicity problem.

Concurrent-access anomalies.

Security problem.

Advantage of DBMS:

Data independency.

Efficient data.

Data administrator.

Concurrent & cress recovery.

Reduce application development time.

Feasibility.

Fast response to information request.

Multi access.

Lest store age.

Advantage of DBMS in brief:

Application program should be as independent as possible from

details of data representation and storage. The DBMS can

provide an abstract view of the data to insulate application

code form such detail.

A DBMS utilize avarety of sophisticated techniques to store

adretrive data efficiently. This feature is especially impotent if

the data is stored on external storage devices.

If data is always accessed through the DBMS, the DBMS can

enforce integrity constrain on the data for example before

inserting on the data for an employee.


When several users share the data cartelization the

administrator of data can offer significant improvements.

Experienced professionals who understand the nature of data

being managed.

A DBMS schedules concurrent access tit hr data in such a

manner that user can think of the data as being accessed by

only one user.

Clearly the DBMS supports many important functions that are

common to many applications accessing store in the DBMS.

Q-5 Consider the following relations. 12.

Myemp(empno,ename,doj,sal,desig)

♫ create table myemp

(

Empno number primary key,

Ename text,

Doj text,

Sal currency,

Design text

);

Project(pcode,pname)

♫ create table project

(

Pcode text primary key,

Pname text

);

Emp_prog(pcode,empno)

♫ create table emp_prog

(

Pcode text references project(pcode),

Empno number references myemp(empno)

);

When we was a create table then we must be insert records and

when we insert records then we must be follow insert command

query it is given as below with example

Syntax :-


Insert into <table name>

Values(value1,value2,value3,……value_n);

Example :-

Insert into myemp

Values(1,’abc’,’01-01-2001’,12000’programmer’);

Insert into project

Values(‘p001’,xyz’);

Insert into emp_prog

Values(‘p001’,’02’);

Ms access is a case sensitive then if you was wrote fields names in

upper or lower case and you may be use that field as a references

then you must be write in same name and same case.

Write a appropriate sql statement for the following :

1. Get the details of employees, whose designation start with an

alphabet ‘p’ and have length of more than 10 characters.

Ans:

2. Get the details of all employees whose designation are

“programmer” and not allocate any project.

Ans:

3. Get the name of an employees who is working on project ‘p001’

and ‘p002’ both

Ans:

4. Get the name of an employees working on project ‘p001’

Ans:

5. Get the details of employees who get minimum salary and

working on project ‘p001’

Ans:

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