Data Base Management System
Content
Data Base Management System (DBMS)
Introduction:
A database system is a computerized record – keeping system. The database itself can be regarded as a kind of electronic filing cabinet: i.e. it is a container for a collection of data files. Users of the system can perform (or request the system to perform, rather) a variety of operations involving such files – for e.g.
Adding new files to the database Inserting data to the existing files Retrieving data from the existing files Deleting data from the existing files Changing data in the existing files Removing existing files from the database
Definition and characteristics of Database Manage System (DBMS):
A Database Management System (DBMS) allows us to enter, store, manipulate, and retrieve information organized into data bases, when a body of information becomes too large or the retrieval demands on it become too complex to manage manually, the information system should be computerized. DBMS provides interactive access to our data bases and provides an easy way to create printed reports.
Database Management Systems are general – purpose programs that dramatically reduce the time necessary to computerize an application. The purpose of a DBMS is to provide two main functions:
1.
2.
A mechanism for organizing, structuring and storing data.
A mechanism for accessing data that provides a measure of data independence, i.e., to some extent it insulates application programs from changes to the data structures.
In data base - oriented approach of organizing data, a set of programs is provided to facilitate users in organizing, creating, deleting, updating, and manipulating data in a database. All these programs together form a Database Management System.
Main components and elements of Database Management System:
Database Management System (DBMS) allows users to organized, process and retrieve selected data from a database without knowing about the underlying database structure.
There are four major components of Database Management System (DBMS) that enables this and these are as follows:
1. Data Definition Language (DDL): Used to define the structure (schema) of the database.
2. Data Manipulation Language (DML): Provides commands to enable the user to enter and manipulate the data. 3. Query Language: Enables users to define their requirements for extracting the desired information from the database in the form of queries. 4. Report generator: Enables the users of the database to design the layout of the report so that it can be presented in the desired format.
Database Models:
Database models define the manner in which the various files of a database are linked together. Four commonly used database models are:
1. Hierarchical 2. Network 3. Relational 4. Sample Report 5. Object – oriented
Hierarchical Database: Data is represented by a tree structure type of organization. The
hierarchical tree specifies what record types are allowed to be included in the data base and the permissible relations between record types. Any record other than the root of the tree must be connected with a superior record, (the parent). To insert a record, the user must select the parent record first, when record is deleted, all the descendents of the record are also deleted. The connections between files don’t depend on the files but defined at the start and are fixed for the life of the data base. These connections are called the structure of the data, looks as an upside down tree. The top file is parent or owner file $ bottom are child or member files. Each parent has at least one child.
A parent element Organization
Personnel Department Finance Department
Technical Department
Managers
Support Staff
Managers
Support Staff
Managers
Engineers
Support Staff
A child element
Network Database: Network model is the generalization of the hierarchical model. A
segment can have multiple parent segments. Many too many logical associations can exist between any two segments $ their instances. The diagrammatic representation is a graph. The network DBMS is like a hierarchical DBMS with 1 modification I. e. one can relate any record types or files with any other record types or files. I.e. date structure is many to many instead of one too many. Here program runs faster.
Fig: Example of Network Database
College
English
Hindi
Math
Computer Science
Seeta
Geeta
Ram
Mohan
Sohan
Raju
A child element can have more than one parent element
This child element has no parent element
Relational: DATA BASE (RDMS) The basic concept of RDBMS was introduced by E. F
codd. In the relational model, the data are viewed as a collection of non hierarchical time varying relations. These are special constructs of mathematical relations & are different from the traditional data processing files & tables. This view of the data enables the user to apply the powerful operations & expressions of relational algebra to data manipulations. It describes data with its natural structure only. It provides a basis for a higher level data language that yields maximal independence between the machine representation & consistency of relations. Accessing & pupation of data can be made simple & efficient. A RDBMS is composed of one or more relations. Each can be visualized as table of data or file Each row (topple) in the relation represents one entity .The value of each column (attribute) is called an item . In any relation no two rows can be identical & the ordering of the rows should not be significant. An attribute or set of attributes whose values uniquely identify a row of a relation is called a key. One is a primary key if there is more than one key. SELECT, PROJECT &JOIN are the three important commands.
Fig: Example of Relational Database Management System (RDBMS)
Membership No 83569
Member’s name K.N. Raina
Member’s Add C-15, Sarita Vihar, Pune-7 A-22, Anand Park, Pune-5 D-18, Vrindavan, Pune-5 A-12, Nandanvan, Pune-2 B-05, Royal Villa, Pune-3 B-16, Anand Park, Pune-5 A-11, Vrindavan, Pune-7
Borrower (Membership No)
Book No (ISBN)
Due Date (DD-MM-YY
62853
D. P. Singh
12859 11348 32228 16185 12859 62853 11348
27-21675-2 89303-530-0 13-201702-5 22-68111-7 71606-214-0 13-48049-8 18-23614-1
10-12-2007 08-11-2007 10-11-2007 05-12-2007 06-11-2007 15-11-2007 12-11-2007
12859
R. Pandey
32228
R. S. Gupta
23466
S. K. Ray
11348
P. K. Sen
16185
T. N. Murli
(a) Members’ data table.
(b) Borrowed books data table.
Book No (ISBN) 13-201702-5 13-48049-8 18-23614-1 22-68111-7 27-21675-2 71606-214-0 89303-530-0
Book Title Concepts of physics Concepts of chemistry Astrology for you Fundamentals of computers C++ Programming Computer Networks Database Systems
Author H. C. Verma S. S. Dubey N. K. Sharma K. Ramesh R. P. Rajan A. K. Rai P. N. Dixit (c ) Books Data table
Sample Report:
List of overdue books as on 10-11-2007
Membership No
Member’s Name
Member’s Add
Due Date
Book NO
Book Title
Book Author
11348
P. K. Sen
B-16, Anand Park, Pune-5
08-11
89303-530-0
Database System
P. N. Dixit
32228
R. S. Gupta
A-12, Nandanvan, Pune-2
10-11
13-201702-5
Concepts of Physics
H. C. Verma
12859
R. Pandey
D-18, Vrindavan, Pune-7
06-11
71606-214-0
Computer Networks
A. N. Rai
A report of overdue books as on 10-11-2007 from the sample database of the previous slide.
Object Oriented Database:
Vehicle
Id Color Specification Manufacturer Length Width Height Engine Type Fuel Type Fuel Tank Capacity
Vehicle specs
Two Wheeler
Four Wheeler
No. of Wheels
Other details of The vehicle like with/ without Gear, seating capacity, etc. Others details of the vehicle like no. of doors, seating capacity etc
Company
Name Location President Id
Employee
Name Age
Domestic Company
Foreign Company
Other details of the company
Other details of the company
Class/ subclass link Attribute/ domain link
Advantages and Disadvantages of Database Management System (DBMS): Advantages:
Advantages of DBMS (Database Management Systems) are followings: A true DBMS offers several advantages over file processing. The principal advantages of a DBMS are the followings: • Flexibility: Because programs and data are independent, programs do not have to be modified when types of unrelated data are added to or deleted from the database, or when physical storage changes. • Fast response to information requests: Because data are integrated into a single database, complex requests can be handled much more rapidly then if the data were located in separate, non-integrated files. In many businesses, faster response means better customer service. • Multiple access: Database software allows data to be accessed in a variety of ways (such as through various key fields) and often, by using several programming languages (both 3GL and nonprocedural 4GL programs). • Lower user training costs: Users often find it easier to learn such systems and training costs may be reduced. Also, the total time taken to process requests may be shorter, which would increase user productivity. • Less storage: Theoretically, all occurrences of data items need be stored only once, thereby
eliminating the storage of redundant data. System developers and database designers often use data normalization to minimize data redundancy
Disadvantages:
Although there are many advantages of DBMS, the DBMS may also have some minor disadvantages. These are:
1. Cost of Hardware & Software: A processor with high speed of data processing and memory of large size is required to run the DBMS software. It means that you have to upgrade the hardware used for file-based system. Similarly, DBMS software is also very costly. 2. Cost of Data Conversion: When a computer file-based system is replaced with a database system, the data stored into data file must be converted to database file. It is very difficult and costly method to convert data of data files into database. You have to hire database and system designers along with application programmers. Alternatively, you have to take the services of some software house. So a lot of money has to be paid for developing software. 3. Cost of Staff Trailing: Most DBMSs are often complex systems so the training for users to use the DBMS is required. Training is required at all levels, including programming, application development, and database administration. The organization has to be paid a lot of amount for the training of staff to run the DBMS. 4. Appointing Technical Staff: The trained technical persons such as database administrator, application programmers, data entry operators etc. are required to handle the DBMS. You have to pay handsome salaries to these persons. Therefore, the" system cost increases.
5. Database Damage: In most of the organizations, all data is integrated into a single database. If database is damaged due to electric failure or database is corrupted on the storage media, then your valuable data may be lost forever.
Conclusion:
A database consists of four elements – data, relationships, constraints and schema. Data are binary computer representations of stored logical entities. Relationships represent a correspondent between the various data elements. Constraints are predicates that define correct database states. Schema describes the organization of data relationships within the database. As we have seen an organization must have accurate, persistent and reliable data for effective decision making. For this purpose, every organization maintains records related to its various operations by building appropriate models of diverse classes of objects. These models capture the inherent properties of these objects and record the relationship among them. Such related data is called a database.
Introduction:
A database system is a computerized record – keeping system. The database itself can be regarded as a kind of electronic filing cabinet: i.e. it is a container for a collection of data files. Users of the system can perform (or request the system to perform, rather) a variety of operations involving such files – for e.g.
Adding new files to the database Inserting data to the existing files Retrieving data from the existing files Deleting data from the existing files Changing data in the existing files Removing existing files from the database
Definition and characteristics of Database Manage System (DBMS):
A Database Management System (DBMS) allows us to enter, store, manipulate, and retrieve information organized into data bases, when a body of information becomes too large or the retrieval demands on it become too complex to manage manually, the information system should be computerized. DBMS provides interactive access to our data bases and provides an easy way to create printed reports.
Database Management Systems are general – purpose programs that dramatically reduce the time necessary to computerize an application. The purpose of a DBMS is to provide two main functions:
1.
2.
A mechanism for organizing, structuring and storing data.
A mechanism for accessing data that provides a measure of data independence, i.e., to some extent it insulates application programs from changes to the data structures.
In data base - oriented approach of organizing data, a set of programs is provided to facilitate users in organizing, creating, deleting, updating, and manipulating data in a database. All these programs together form a Database Management System.
Main components and elements of Database Management System:
Database Management System (DBMS) allows users to organized, process and retrieve selected data from a database without knowing about the underlying database structure.
There are four major components of Database Management System (DBMS) that enables this and these are as follows:
1. Data Definition Language (DDL): Used to define the structure (schema) of the database.
2. Data Manipulation Language (DML): Provides commands to enable the user to enter and manipulate the data. 3. Query Language: Enables users to define their requirements for extracting the desired information from the database in the form of queries. 4. Report generator: Enables the users of the database to design the layout of the report so that it can be presented in the desired format.
Database Models:
Database models define the manner in which the various files of a database are linked together. Four commonly used database models are:
1. Hierarchical 2. Network 3. Relational 4. Sample Report 5. Object – oriented
Hierarchical Database: Data is represented by a tree structure type of organization. The
hierarchical tree specifies what record types are allowed to be included in the data base and the permissible relations between record types. Any record other than the root of the tree must be connected with a superior record, (the parent). To insert a record, the user must select the parent record first, when record is deleted, all the descendents of the record are also deleted. The connections between files don’t depend on the files but defined at the start and are fixed for the life of the data base. These connections are called the structure of the data, looks as an upside down tree. The top file is parent or owner file $ bottom are child or member files. Each parent has at least one child.
A parent element Organization
Personnel Department Finance Department
Technical Department
Managers
Support Staff
Managers
Support Staff
Managers
Engineers
Support Staff
A child element
Network Database: Network model is the generalization of the hierarchical model. A
segment can have multiple parent segments. Many too many logical associations can exist between any two segments $ their instances. The diagrammatic representation is a graph. The network DBMS is like a hierarchical DBMS with 1 modification I. e. one can relate any record types or files with any other record types or files. I.e. date structure is many to many instead of one too many. Here program runs faster.
Fig: Example of Network Database
College
English
Hindi
Math
Computer Science
Seeta
Geeta
Ram
Mohan
Sohan
Raju
A child element can have more than one parent element
This child element has no parent element
Relational: DATA BASE (RDMS) The basic concept of RDBMS was introduced by E. F
codd. In the relational model, the data are viewed as a collection of non hierarchical time varying relations. These are special constructs of mathematical relations & are different from the traditional data processing files & tables. This view of the data enables the user to apply the powerful operations & expressions of relational algebra to data manipulations. It describes data with its natural structure only. It provides a basis for a higher level data language that yields maximal independence between the machine representation & consistency of relations. Accessing & pupation of data can be made simple & efficient. A RDBMS is composed of one or more relations. Each can be visualized as table of data or file Each row (topple) in the relation represents one entity .The value of each column (attribute) is called an item . In any relation no two rows can be identical & the ordering of the rows should not be significant. An attribute or set of attributes whose values uniquely identify a row of a relation is called a key. One is a primary key if there is more than one key. SELECT, PROJECT &JOIN are the three important commands.
Fig: Example of Relational Database Management System (RDBMS)
Membership No 83569
Member’s name K.N. Raina
Member’s Add C-15, Sarita Vihar, Pune-7 A-22, Anand Park, Pune-5 D-18, Vrindavan, Pune-5 A-12, Nandanvan, Pune-2 B-05, Royal Villa, Pune-3 B-16, Anand Park, Pune-5 A-11, Vrindavan, Pune-7
Borrower (Membership No)
Book No (ISBN)
Due Date (DD-MM-YY
62853
D. P. Singh
12859 11348 32228 16185 12859 62853 11348
27-21675-2 89303-530-0 13-201702-5 22-68111-7 71606-214-0 13-48049-8 18-23614-1
10-12-2007 08-11-2007 10-11-2007 05-12-2007 06-11-2007 15-11-2007 12-11-2007
12859
R. Pandey
32228
R. S. Gupta
23466
S. K. Ray
11348
P. K. Sen
16185
T. N. Murli
(a) Members’ data table.
(b) Borrowed books data table.
Book No (ISBN) 13-201702-5 13-48049-8 18-23614-1 22-68111-7 27-21675-2 71606-214-0 89303-530-0
Book Title Concepts of physics Concepts of chemistry Astrology for you Fundamentals of computers C++ Programming Computer Networks Database Systems
Author H. C. Verma S. S. Dubey N. K. Sharma K. Ramesh R. P. Rajan A. K. Rai P. N. Dixit (c ) Books Data table
Sample Report:
List of overdue books as on 10-11-2007
Membership No
Member’s Name
Member’s Add
Due Date
Book NO
Book Title
Book Author
11348
P. K. Sen
B-16, Anand Park, Pune-5
08-11
89303-530-0
Database System
P. N. Dixit
32228
R. S. Gupta
A-12, Nandanvan, Pune-2
10-11
13-201702-5
Concepts of Physics
H. C. Verma
12859
R. Pandey
D-18, Vrindavan, Pune-7
06-11
71606-214-0
Computer Networks
A. N. Rai
A report of overdue books as on 10-11-2007 from the sample database of the previous slide.
Object Oriented Database:
Vehicle
Id Color Specification Manufacturer Length Width Height Engine Type Fuel Type Fuel Tank Capacity
Vehicle specs
Two Wheeler
Four Wheeler
No. of Wheels
Other details of The vehicle like with/ without Gear, seating capacity, etc. Others details of the vehicle like no. of doors, seating capacity etc
Company
Name Location President Id
Employee
Name Age
Domestic Company
Foreign Company
Other details of the company
Other details of the company
Class/ subclass link Attribute/ domain link
Advantages and Disadvantages of Database Management System (DBMS): Advantages:
Advantages of DBMS (Database Management Systems) are followings: A true DBMS offers several advantages over file processing. The principal advantages of a DBMS are the followings: • Flexibility: Because programs and data are independent, programs do not have to be modified when types of unrelated data are added to or deleted from the database, or when physical storage changes. • Fast response to information requests: Because data are integrated into a single database, complex requests can be handled much more rapidly then if the data were located in separate, non-integrated files. In many businesses, faster response means better customer service. • Multiple access: Database software allows data to be accessed in a variety of ways (such as through various key fields) and often, by using several programming languages (both 3GL and nonprocedural 4GL programs). • Lower user training costs: Users often find it easier to learn such systems and training costs may be reduced. Also, the total time taken to process requests may be shorter, which would increase user productivity. • Less storage: Theoretically, all occurrences of data items need be stored only once, thereby
eliminating the storage of redundant data. System developers and database designers often use data normalization to minimize data redundancy
Disadvantages:
Although there are many advantages of DBMS, the DBMS may also have some minor disadvantages. These are:
1. Cost of Hardware & Software: A processor with high speed of data processing and memory of large size is required to run the DBMS software. It means that you have to upgrade the hardware used for file-based system. Similarly, DBMS software is also very costly. 2. Cost of Data Conversion: When a computer file-based system is replaced with a database system, the data stored into data file must be converted to database file. It is very difficult and costly method to convert data of data files into database. You have to hire database and system designers along with application programmers. Alternatively, you have to take the services of some software house. So a lot of money has to be paid for developing software. 3. Cost of Staff Trailing: Most DBMSs are often complex systems so the training for users to use the DBMS is required. Training is required at all levels, including programming, application development, and database administration. The organization has to be paid a lot of amount for the training of staff to run the DBMS. 4. Appointing Technical Staff: The trained technical persons such as database administrator, application programmers, data entry operators etc. are required to handle the DBMS. You have to pay handsome salaries to these persons. Therefore, the" system cost increases.
5. Database Damage: In most of the organizations, all data is integrated into a single database. If database is damaged due to electric failure or database is corrupted on the storage media, then your valuable data may be lost forever.
Conclusion:
A database consists of four elements – data, relationships, constraints and schema. Data are binary computer representations of stored logical entities. Relationships represent a correspondent between the various data elements. Constraints are predicates that define correct database states. Schema describes the organization of data relationships within the database. As we have seen an organization must have accurate, persistent and reliable data for effective decision making. For this purpose, every organization maintains records related to its various operations by building appropriate models of diverse classes of objects. These models capture the inherent properties of these objects and record the relationship among them. Such related data is called a database.
