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DATA BASED MANAGEMENT SYSTEMS

INTRODUCTION

• The DBMS provides users and programmers with a systamatic way to create ,retrieve,update and manage data.
• DBMS is a system software for creating and managing data bases.

DATA BASE SYSTEM

• The Grouping  of database and, DBMS software together is known as database system
• A database system is a computer software application that interacts with the user ,and database by its own capture and analyze data.
• The Basic purpose DBMS is designed to allow the administration of databases,creation,defination,update,querying.
• It is a technology of storing and retrieving user's data with standard security measures.

CHARACTERISTICS OF DBMS

• DBMS  can store any kind of data
• In DBMS, users have a chance to access the data at the same time 
• Data integrity ,it is the most important characteristics of database management system ->Data integrity deals with quality and reliability of database system
• DBMS includes structures and described data
• DBMS represents complex relationship between data 
• DBMS have recovery and backup property
• DBMS support ACID properties

       A-Accuracy 
       C-Completeness
        I- Isolation
       D-Durability

• Automatic recovery feature has to be provided to overcome the problems with processing system failure
• To incorporate the requirements of the organization,system should be designed for easy maintenance
• Information systems should allow interactive access to data to obtain new information without writing fresh programs 
• System should be designed to co-relate different data to meet new requirements 
• An independent central repository ,which gives information and meaning of available data is required.

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DATABASE VS  FILE SYSTEM

File system

1. File system is a collection of data, any management with the file system ,user has to write the procedures
2. File system gives the details of the data representation and storage of data
3. File system doesn't provide crash recovery mechanism 

       eg: when you are entering any kind of data  into the file,if                      system crashes then content of the file is lost 

     4. In File system storing and retrieving of data cannot be done              efficiently
     5. concurrent access to the data in the file system has many                    problems like reading file while other deleting some                          information, updating some information 
     6. protecting a file under file system is very difficult

DBMS

1. DBMS is a collection of data and user is not required to write the procedures for managing the database
2. DBMS provides an abstract view of data that hides the details
3. DBMS has crash recovery mechanism ,DBMS protects user from the effects of system failures
4. DBMS is efficient to use since there are wide varieties of sophisticated techniques to store and retrieve the data
5. DBMS takes care of concurrent access using some from of locking 
6. DBMS has a good protection mechanism 

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DATABASE USERS

•    Database users are the one who really use and take the benifits of database.
• Depending on the accessing database ,there are different types of users.

End Users:

• These are persons who access the Database for querying ,updating and report generation.
• End users are the main reason for database existence

Casual end useers:

• use database occasionally ,needing different information each time,use query language to specify their requests ,typically middle or high level managers

Application Programmers

• The developers who interact with the database by means of DML queries.These DML queries are written in the application programs like C,C++ ,JAVA etc.
• These queries are converted into object code to communicate with the database.
• The application programmer is responsible for designing and testing program logic,coding programs,preparation of programs for computer operations and program documentation .

  Example:

• Writting a C program to generate the report of students who are studying in particular college will involve a query to fetch the data from database ,it will include a embedded SQL query in the C program.

Native user's

• Any user who does not have any knowledge about database can be in this category.
• These Native users use the existing application  to interact with the database and there task is to just use the already developed application and get the desired results.
• these users have existing application and users use them to interact with the database to fulfill their requests. 

 Example:

• ticket booking systems,ATM's, Online Shopping System etc;

Specialized Users

• specialized users are sophisticated users writing special database application programs, specialized users are the developers who develop the complex programs to the requirement.

 Example: 

   CADD Systems ,expert systems ,complex data  systems (format video/audio),knowledge-based  systems etc;

Sophisticated users

• sophisticated users are database developers,who write SQL queries to select/update/delete/insert data.
• sophisticated users do not use any application or programs to request the database .
• These users interact with the system without writing programs
• sophisticated users form requests by writing queries in a database query language ,these are then submitted to a query processor that breaks a DML statement down into instructions for the database manager module

Stand-alone Users

• These are the users who maintain their personal database using ready made Software which is available in the market easily and provide the menu based interface through which they can easily used the database
• stand-alone users have ready made database packages which will have menus and graphical interfaces.

Actors on the Scene

Those who actually use and control the database content,and who deign ,develop and maintain database applications are called"Actors on the Scene".

Those who design and develop the DBMS software and related tools,and the compiler systems operators are called "Workers behind the Scene".

Database Administrator (DBA)

• DBA is the chief administrator ,who oversees and manages the database system,This DBA is mainly concerned with installing, and maintaining DBMS servers.
• Database Administrators Prime tasks are security ,installing,recovery,backups,replications,memory management ,tuning and Configurations.
• In Large Organizations the DBA might have a support staff.
• Database Administrator mainly responsible for all administrative tasks of a database including the data and software.

Database Designers:

• Database Designers are responsible for identifying the data to be stored and for choosing an appropriate way to organize it.

System Analysts:

• These system analysts determine needs of end users ,especially native and parametric users, and develop specifications for canned transcations that meet these needs.

Workers behind the Scene: 

DBMS System designers /implementors:

• These designers provide the DBMS software that is at the foundation of all this.

TOOL developers:

• Tool developers design and implement software tools faciliating database system Design,performance monitoring,creation of graphical user interfaces , prototyping etc.

Operators and maintenance personnel:

• These operators responsible for the day-to-day operation of the system. 

Types of DBA

 There are different kinds of DBA depending on the responsibility that he owns.

• Administrative DBA - This DBA is mainly concerned with installing, and maintaining DBMS servers. His prime tasks are installing, backups, recovery, security, replications, memory management, configurations and tuning. He is mainly responsible for all administrative tasks of a database.

• Development DBA - He is responsible for creating queries and procedure for the requirement. Basically his task is similar to any database developer.

• Database Architect - Database architect is responsible for creating and maintaining the users, roles, access rights, tables, views, constraints and indexes. He is mainly responsible for designing the structure of the database depending on the requirement. These structures will be used by developers and development DBA to code.

• Data Warehouse DBA -DBA should be able to maintain the data and procedures from various sources in the datawarehouse. These sources can be files, COBOL, or any other programs. Here data and programs will be from different sources. A good DBA should be able to keep the performance and function levels from these sources at same pace to make the datawarehouse to work.

• Application DBA -He acts like a bridge between the application program and the database. He makes sure all the application program is optimized to interact with the database. He ensures all the activities from installing, upgrading, and patching, maintaining, backup, recovery to executing the records works without any issues.

• OLAP DBA - He is responsible for installing and maintaining the database in OLAP systems. He maintains only OLAP databases.

Database Administrators 

The life cycle of database starts from designing, implementing to administration of it. A database for any kind of requirement needs to be designed perfectly so that it should work without any issues. Once all the design is complete, it needs to be installed. Once this step is complete, users start using the database. The database grows as the data grows in the database. When the database becomes huge, its performance comes down. Also accessing the data from the database becomes challenge. There will be unused memory in database, making the memory inevitably huge. These administration and maintenance of database is taken care by database Administrator – DBA.
A DBA has many responsibilities. A good performing database is in the hands of DBA.

• Installing and upgrading the DBMS Servers: - DBA is responsible for installing a new DBMS server for the new projects. He is also responsible for upgrading these servers as there are new versions comes in the market or requirement. If there is any failure in upgradation of the existing servers, he should be able revert the new changes back to the older version, thus maintaining the DBMS working. He is also responsible for updating the service packs/ hot fixes/ patches to the DBMS servers.

• Design and implementation: - Designing the database and implementing is also DBA’s responsibility. He should be able to decide proper memory management, file organizations, error handling, log maintenance etc for the database.

• Performance tuning: - Since database is huge and it will have lots of tables, data, constraints and indices, there will be variations in the performance from time to time. Also, because of some designing issues or data growth, the database will not work as expected. It is responsibility of the DBA to tune the database performance. He is responsible to make sure all the queries and programs works in fraction of seconds.

• Migrate database servers: - Sometimes, users using oracle would like to shift to SQL server or Netezza. It is the responsibility of DBA to make sure that migration happens without any failure, and there is no data loss.

• Backup and Recovery: - Proper backup and recovery programs needs to be developed by DBA and has to be maintained him. This is one of the main responsibilities of DBA. Data/objects should be backed up regularly so that if there is any crash, it should be recovered without much effort and data loss.

• Security: - DBA is responsible for creating various database users and roles, and giving them different levels of access rights.

• Documentation: - DBA should be properly documenting all his activities so that if he quits or any new DBA comes in, he should be able to understand the database without any effort. He should basically maintain all his installation, backup, recovery, security methods. He should keep various reports about database performance.

In order to perform his entire task, he should have very good command over DBMS.
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Advantage and Disadvantages of DBMS

"A database management system (DBMS) is a collection of programs that manages the database structure and controls access to the data stored in thedatabase". The DBMS serves as the intermediary between the user and thedatabase. ... Here, Let's find database management system advantages and disadvantages.

Advantage and Disadvantages of DBMS

Advantage of DBMS

1. Improved data sharing:

• The DBMS helps create an environment in which end users have better access to more and better-managed data.
• Such access makes it possible for end users to respond quickly to changes in their environment.

2. Improved data security:

• The more users access the data, the greater the risks of data security breaches.Corporations invest considerable amounts of time, effort, and money to ensure that corporate data are used properly.
• A DBMS provides a framework for better enforcement of data privacy and security policies.

3. Better data integration:

• Wider access to well-managed data promotes an integrated view of the organization’s operations and a clearer view of the big picture.
• It becomes much easier to see how actions in one segment of the company affect other segments.

4. Minimized data inconsistency:

• Data inconsistency exists when different versions of the same data appear in different places.
• For example, data inconsistency exists when a company’s sales department stores a sales representative’s name as “Bill Brown” and the company’s personnel department stores that same person’s name as “William G. Brown,” or when the company’s regional sales office shows the price of a product as $47.95 and its national sales office shows the same product’s price as $45.95.
• The probability of data inconsistency is greatly reduced in a properly designed database.

5. Improved data access:

• The DBMS makes it possible to produce quick answers to ad hoc queries.
• From a database perspective, a query is a specific request issued to the DBMS for data manipulation—for example, to read or update the data. Simply put, a query is a question, and an ad hoc query is a spur-of-the-moment question.
• The DBMS sends back an answer (called the query result set) to the application.
• For example, end users

6. Improved decision making:

• Better-managed data and improved data access make it possible to generate better-quality information, on which better decisions are based.
• The quality of the information generated depends on the quality of the underlying data.
• Data quality is a comprehensive approach to promoting the accuracy, validity, and timeliness of the data. While the DBMS does not guarantee data quality, it provides a framework to facilitate data quality initiatives.
• Increased end-user productivity
• The availability of data, combined with the tools that transform data into usable information, empowers end users to make quick, informed decisions that can make the difference between success and failure in the global economy.

Disadvantage of DBMS

1. Increased costs:

• Database systems require sophisticated hardware and software and highly skilled personnel.
• The cost of maintaining the hardware, software, and personnel required to operate and manage a database system can be substantial. Training, licensing, and regulation compliance costs are often overlooked when database systems are implemented.

2. Management complexity:

• Database systems interface with many different technologies and have a significant impact on a company’s resources and culture.
• The changes introduced by the adoption of a database system must be properly managed to ensure that they help advance the company’s objectives. Given the fact that database systems hold crucial company data that are accessed from multiple sources, security issues must be assessed constantly.

3. Maintaining currency:

• To maximize the efficiency of the database system, you must keep your system current.
• Therefore, you must perform frequent updates and apply the latest patches and security measures to all components.
• Because database technology advances rapidly, personnel training costs tend to be significant. Vendor dependence.
• Given the heavy investment in technology and personnel training, companies might be reluctant to change database vendors.

4. Frequent upgrade/replacement cycles:

• DBMS vendors frequently upgrade their products by adding new functionality. Such new features often come bundled in new upgrade versions of the software.
• Some of these versions require hardware upgrades. Not only do the upgrades themselves cost money, but it also costs money to train database users and administrators to properly use and manage the new features.

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Database Application'S:

SOME APPLICATIONS OF DBMS

A database application is a computer program whose primary purpose is entering and retrieving information from a computerized database. Early examples ofdatabase applications were accounting systems and airline reservations systems, such as SABRE, developed starting in 1957.

Purpose of Database Applications

Database applications are used to search, sort, calculate, report and share information. Databases can also contain code to perform mathematical and statistical calculations on the data to support queries submitted by users. Database applications provide security by restricting access to data based upon user names and passwords. Most database applications are customized with a database programming language to automate specific types of work.

• Telecom: There is a database to keeps track of the information regarding calls made, network usage, customer details etc. Without the database systems it is hard to maintain that huge amount of data that keeps updating every millisecond.

• Industry: Where it is a manufacturing unit, warehouse or distribution centre, each one needs a database to keep the records of ins and outs. For example distribution centre should keep a track of the product units that supplied into the centre as well as the products that got delivered out from the distribution centre on each day; this is where DBMS comes into picture.

• Banking System: For storing customer info, tracking day to day credit and debit transactions, generating bank statements etc. All this work has been done with the help of Database management systems.

• Education sector: Database systems are frequently used in schools and colleges to store and retrieve the data regarding student details, staff details, course details, exam details, payroll data, attendance details, fees details etc. There is a hell lot amount of inter-related data that needs to be stored and retrieved in an efficient manner.

• Online shopping: You must be aware of the online shopping websites such as Amazon, Flipkart etc. These sites store the product information, your addresses and preferences, credit details and provide you the relevant list of products based on your query. All this involves a Database management system.

Accounting Applications

An accounting system is a custom database application used to manage financial data. Custom forms are used to record assets, liabilities, inventory and the transactions between customers and suppliers. The income statements, balance sheets, purchase orders and invoices generated are custom reports based upon information that is entered into the database. Accounting applications can run on a single computer suitable for a small business or in a networked shared environment to accommodate the needs of multiple departments and locations in larger organizations. "Microsoft Money," "Quicken," "QuickBooks" and "Peachtree" are accounting systems built upon database applications.

CRM Applications

A customer relationship management system (CRM) is another example of a database application that has been customized to manage the marketing, sales, and support relationships between a business and it's customers. The ultimate goal is to maximize sales, minimize costs and foster strategic customer relationships. Simple contact management programs such as "ACT," or the task manager in Microsoft's "Outlook" can be customized to suit the needs of individuals and small businesses. "SAP," "Salesforce.com," and Oracle's "Siebel" are robust CRM database applications suitable for larger enterprises.

Web Applications

Many contemporary web sites are built using several database applications simultaneously as core components. Most retail store Web sites including Amazon.com
& Flipkart.com use database systems to store, update and present data about products for sale. These Web sites also combine an accounting database system to record sales transactions and a CRM database application to incorporate feedback and drive a positive customer experience. The popular Web-based "Facebook" application is essentially a database built upon the "MySQL" database system and is an indication of the increasing usage of database applications as foundations for Web-based applications.

------------------------------------------------------------ Definitions to be remember & Main Key Points

WHAT IS A DATABASE MANAGEMENT  SYSTEM

A database management system (DBMS) is system software for creating and managing databases. The DBMS provides users and programmers with a systematic way to create, retrieve, update and manage data.

A database management system (DBMS) is a computer software application that interacts with the user, other applications, and the database itself to capture and analyze data. A general-purpose DBMS is designed to allow the definition, creation, querying, update, and administration of databases.

Why do we use a database management system?

DBMS stands for database management system; in other words, a system that manages databases. Examples of DBMSes are Oracle and SQL Server. These are systems that can be used to manage transactional databases, such as HR systems, banking systems and so on. These are typically optimized for performing transactions.

What is an example of a database?

A Microsoft Excel spreadsheet or Microsoft Access are good examples of desktopdatabase programs. These programs allow users to enter data, store it, protect it, and retrieve it when needed. ... They include databases like SQL Server, OracleDatabase, Sybase, Informix, and MySQL

What is a database development?

A core aspect of software engineering is the subdivision of the developmentprocess into a series of phases, or steps, each of which focuses on one aspect of the development. The collection of these steps is sometimes referred to as adevelopment life cycle.

What is meant by SQL database?

SQL is used to communicate with a database. According to ANSI (American National Standards Institute), it is the standard language for relational database management systems. SQL statements are used to perform tasks such as update data on a database, or retrieve data from a database.

What is a database for a computer?

(1) Often abbreviated DB, a database is basically a collection of information organized in such a way that a computer program can quickly select desired pieces of data. You can think of a database as an electronic filing system. Traditionaldatabases are organized by fields, records, and files.

What are the types of database management system?

There are four structural types of database management systems:

• Hierarchical databases.
• Network databases.
• Relational databases.
• Object-oriented databases.

What is an example of a DBMS?

Some DBMS examples include MySQL, PostgreSQL, Microsoft Access, SQL Server, FileMaker, Oracle, RDBMS, dBASE, Clipper, and FoxPro. Since there are so many database management systems available, it is important for there to be a way for them to communicate with each other.

What is a data base?

A database is a collection of information organized to provide efficient retrieval. The collected information could be in any number of formats (electronic, printed, graphic, audio, statistical, combinations). There are physical (paper/print) and electronicdatabases.

What is the use of a database?

Uses for database systems. Uses for database systems include: They store data. They store special information used to manage the data

What is a relational database management system?

A relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as invented by E. F. Codd, of IBM's San Jose Research Laboratory. In 2017, many of the databases in widespread use are based on the relational database model.

Why is it important for a business to have a database?

A database management system is important because it manages data efficiently and allows users to perform multiple tasks with ease. A database management system stores, organizes and manages a large amount of information within a single software application.

What is the purpose of a database management system?

Organizations use large amounts of data. A database management system(DBMS) is a software tool that makes it possible to organize data in a database. ... The ultimate purpose of a database management system is to store and transform data into information to support making decisions.

What is the use of database software?

Sometimes referred to as database management systems (DBMS), database software tools are primarily used for storing, modifying, extracting, and searching for information within a database.

What is a database package?

Packages. A package is a group of related procedures and functions, together with the cursors and variables they use, stored together in the database for continued use as a unit. Similar to standalone procedures and functions, packaged procedures and functions can be called explicitly by applications or users.

What is the database design?

Database design is the process of producing a detailed data model of database. ... A fully attributed data model contains detailed attributes for each entity. The termdatabase design can be used to describe many different parts of the design of an overall database system.

What is the meaning of structured query language?

Structured Query Language (SQL) is a standard computer language for relational database management and data manipulation. SQL is used to query, insert, update and modify data.

What is meant by SQL Server?

SQL Server is Microsoft's relational database management system (RDBMS). It is a full-featured database primarily designed to compete against competitors Oracle Database (DB) and MySQL. Like all major RBDMS, SQL Server supports ANSISQL, the standard SQL language.

What is a traditional data base?

Data generation is skyrocketing—traditional database systems fail to support “big data” “Big data” encompass a wide range of the tremendous data generated from various sources such as mobile devices, digital repositories, and enterprise applications. The data can be structured as well as unstructured.

What is a table in a database?

In relational databases, and flat file databases, a table is a set of data elements (values) using a model of vertical columns (identifiable by name) and horizontal rows, the cell being the unit where a row and column intersect. A table has a specified number of columns, but can have any number of rows.

What are some databases?

Established:

• DB2.
• MySQL.
• Oracle.
• PostgreSQL.
• SQLite.
• SQL Server.
• Sybase.

What is a relational database?

A relational database is a collection of data items organized as a set of formally-described tables from which data can be accessed or reassembled in many different ways without having to reorganize the database tables. The relational database was invented by E. F. Codd at IBM in 1970.

Is SQL a DBMS?

Unlike network DBMS, RDBMS does not support many to many relationships.Relational DBMS usually have pre-defined data types that they can support. This is the most popular DBMS type in the market. Examples of relational database management systems include MySQL, Oracle, and Microsoft SQL Server database.

What is a database in business?

A database is an organized collection of information. Small businesses can usedatabases in a number of different ways. A database can help you organize information about your customers and clients. A database can contain information about your product inventory.

What are the functions of a database management system?

The ten functions in the DBMS are: data dictionary management, data storage management, data transformation and presentation, security management, multiuser access control, backup and recovery management, data integrity management, database access languages and application programming interfaces, database communication ...

What is the definition of Rdbms?

RDBMS is the basis for SQL, and for all modern database systems like MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access. A Relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as introduced by E. F. Codd.

What is the difference between DBMS and Rdbms?

Key Difference between DBMS and RDBMS: The key difference is that RDBMS(relational database management system) applications store data in a tabular form, while DBMS applications store data as files. ... There can be, but there will be no “relation” between the tables, like in a RDBMS.

What is the relational database model?

The relational model (RM) for database management is an approach to managingdata using a structure and language consistent with first-order predicate logic, first described in 1969 by Edgar F. Codd, where all data is represented in terms of tuples, grouped into relations.

How do databases generate sales and profits?

Marketing databases do not generate revenue by themselves. They must be used in an active program of profitability analysis, customer segmentation, and marketing tactics that build retention, loyalty, and increased sales.

How databases are used?

Database uses. ... A hospital will store details of all its patients in a database, eg a history of their health issues. The Government uses a database to store records of people's income tax payments. A database is used to keep track of all the drivers in central London who have (or haven't) paid the Congestion Charge.

What is meant by Ordbms?

An object-relational database (ORD), or object-relational database management system (ORDBMS), is a database management system (DBMS) similar to a relational database, but with an object-oriented database model: objects, classes and inheritance are directly supported in database schemas and in the query language.

Is Oracle database Rdbms?

Oracle Database (commonly referred to as Oracle RDBMS or simply as Oracle) is an object-relational database management system produced and marketed byOracle Corporation.

What is a database program?

A database program is the heart of a business information system and provides file creation, data entry, update, query and reporting functions. The traditional term fordatabase software is "database management system" .

What is a query in a database?

A query is an inquiry into the database using the SELECT statement. A query is used to extract data from the database in a readable format according to the user's request. For instance, if you have an employee table, you might issue a SQL statement that returns the employee who is paid the most.

What is the package in Oracle?

A package is a schema object that groups logically related PL/SQL types, variables, constants, subprograms, cursors, and exceptions. A package is compiled and stored in the database, where many applications can share its contents.

What is a package in PL SQL?

What Is a PL/SQL Package? A package is a schema object that groups logically related PL/SQL types, variables, and subprograms. Packages usually have two parts, a specification (spec) and a body; sometimes the body is unnecessary. The specification is the interface to the package.

What is the use of cursor in Oracle?

Oracle creates a memory area, known as the context area, for processing an SQL statement, which contains all the information needed for processing the statement; for example, the number of rows processed, etc. A cursor is a pointer to this context area. PL/SQL controls the context area through a cursor.

How do you create a relational database?

1. Step 1: Define the Purpose of the Database (Requirement Analysis) Gather the requirements and define the objective of your database, e.g. ... ...
2. Step 2: Gather Data, Organize in tables and Specify the Primary Keys. ...
3. Step 3: Create Relationships among Tables. ...
4. Step 4: Refine & Normalize the Design.

Who created SQL?

SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce in the early 1970s.

Why is it called Structured Query Language?

SQL is a standardized query language for requesting information from a database. The original version called SEQUEL (structured English query language) was designed by an IBM research center in 1974 and 1975. SQL was first introduced as a commercial database system in 1979 by Oracle Corporation.

What is a database development?

A core aspect of software engineering is the subdivision of the developmentprocess into a series of phases, or steps, each of which focuses on one aspect of the development. The collection of these steps is sometimes referred to as adevelopment life cycle.

What are the different types of databases?

Relational databases are the most common database systems. They include databases like SQL Server, Oracle Database, Sybase, Informix, and MySQL. Therelational database management systems (RDMS) feature much better performance for managing data over desktop database programs.

What is the catalog in a database?

In computing, a catalog is a directory of information about data sets, files, or adatabase . A catalog usually describes where a data set, file or database entity is located and may also include other information, such as the type of device on which each data set or file is stored.

What is the difference between data and information?

Data are simply facts or figures — bits of information, but not information itself. When data are processed, interpreted, organized, structured or presented so as to make them meaningful or useful, they are called information. Information provides context for data.

What is the architecture of a database?

The database architecture is the set of specifications, rules, and processes that dictate how data is stored in a database and how data is accessed by components of a system. It includes data types, relationships, and naming conventions.

What do you mean by Oracle?

Oracle database (Oracle DB) is a relational database management system (RDBMS) from the Oracle Corporation. Originally developed in 1977 by Lawrence Ellison and other developers, Oracle DB is one of the most trusted and widely-used relational database engines.

What is the database server?

A database server is a computer program that provides database services to other computer programs or to computers, as defined by the client–server model. The term may also refer to a computer dedicated to running such a program. ... Mostdatabase servers respond to a query language.

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Different Data Models In DBMS


What is a database model?

A database model is a type of data model that determines the logical structure of a database and fundamentally determines in which manner data can be stored, organized and manipulated. The most popular example of a database model is the relational model, which uses a table-based format.
                              (or)
A database model shows the logical structure of a database, including the relationships and constraints that determine how data can be stored and accessed. Individual database models are designed based on the rules and concepts of whichever broader data model the designers adopt. Most data models can be represented by an accompanying database diagram.

What are the different types of data models?

• Hierarchical database model.
• Relational model.
• Network model.
• Object-oriented database model.
• Entity-relationship model.
• Document model.
• Entity-attribute-value model.
• Star schema.

What is hierarchical data model in DBMS?

A hierarchical database model is a data model in which the data is organized into a tree-like structure. The data is stored as records which are connected to one another through links. A record is a collection of fields, with each field containing only one value.

hierachical data model

hierachical data model

hierachical data model

What is network data model in DBMS?

The network model is a database model conceived as a flexible way of representing objects and their relationships. Its distinguishing feature is that the schema, viewed as a graph in which object types are nodes and relationship types are arcs, is not restricted to being a hierarchy or lattice.

Network model

What is Relational Data Model in DBMS?

The relational model (RM) for database management is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in 1969 by Edgar F.Codd, where all data is represented in terms of tuples, grouped into relations.

                                           relational model

What is parent child relationship in database?
Child tables and parent tables are just normal database tables, but they're linked in a way that's described by a parent–child relationship. It's usually used to specify where one table's value refers to the value in another table (usually a primary key of another table). For example, imagine a news article.

What is the hierarchy of data in a database?
Data hierarchy refers to the systematic organization of data, often in a hierarchical form. Data organization involves characters, fields, records, files and so on. A data field holds a single fact or attribute of an entity.

What is an object oriented data model?
An object database (also object-oriented database management system, OODBMS) is a database management system in which information is represented in the form of objects as used in object-oriented programming. Object databases are different from relational databases which are table-oriented.

Other database models

Inverted file model
A database built with the inverted file structure is designed to facilitate fast full text searches. In this model, data content is indexed as a series of keys in a lookup table, with the values pointing to the location of the associated files. This structure can provide nearly instantaneous reporting in big data and analytics, for instance.

This model has been used by the ADABAS database management system of Software AG since 1970, and it is still supported today.

Flat model
The flat model is the earliest, simplest data model. It simply lists all the data in a single table, consisting of columns and rows. In order to access or manipulate the data, the computer has to read the entire flat file into memory, which makes this model inefficient for all but the smallest data sets.

Multidimensional model
This is a variation of the relational model designed to facilitate improved analytical processing. While the relational model is optimized for online transaction processing (OLTP), this model is designed for online analytical processing (OLAP).

Each cell in a dimensional database contains data about the dimensions tracked by the database. Visually, it’s like a collection of cubes, rather than two-dimensional tables.

Semi structured model
In this model, the structural data usually contained in the database schema is embedded with the data itself. Here the distinction between data and schema is vague at best. This model is useful for describing systems, such as certain Web-based data sources, which we treat as databases but cannot constrain with a schema. It’s also useful for describing interactions between databases that don’t adhere to the same schema.

Context model
This model can incorporate elements from other database models as needed. It cobbles together elements from object-oriented, semistructured, and network models.

Associative model
This model divides all the data points based on whether they describe an entity or an association. In this model, an entity is anything that exists independently, whereas an association is something that only exists in relation to something else.

The associative model structures the data into two sets:

• A set of items, each with a unique identifier, a name, and a type
• A set of links, each with a unique identifier and the unique identifiers of a source, verb, and target. The stored fact has to do with the source, and each of the three identifiers may refer either to a link or an item.

Other, less common database models include:
-->Semantic model, which includes information about           how the stored data relates to the real world.
-->XML database, which allows data to be specified            and even stored in XML format.
-->Named graph
-->Triplestore

NoSQL database models

In addition to the object database model, other non-SQL models have emerged in contrast to the relational model:
The graph database model, which is even more flexible than a network model, allowing any node to connect with any other.
The multi value model, which breaks from the relational model by allowing attributes to contain a list of data rather than a single data point.
The document model, which is designed for storing and managing documents or semi-structured data, rather than atomic data.
------------------------------------------------------------------------ some important concepts to learn

What is a table in a database?
In relational databases, and flat file databases, a table is a set of data elements (values) using a model of vertical columns (identifiable by name) and horizontal rows, the cell being the unit where a row and column intersect. A table has a specified number of columns, but can have any number of rows.

What is a relation in database?
A relational database is a set of tables containing data fitted into predefined categories. Each table (which is sometimes called a relation) contains one or more data categories in columns. Each row contains a unique instance of data for the categories defined by the columns.

What is a tuple in a database?
Tuples are known values which is used to relate the table in relational DB. ... As I understand it a table has a set K of keys and a typing function T with domain K. A row, or "tuple", of the table is a function r with domain K such that r(k) is an element of T(k) for each key k.

What is an example of a relational database?
There are also many free and open-source RDBMS, such as MySQL, mSQL (mini-SQL) and the embedded JavaDB (Apache Derby). A relational database organizes data in tables (or relations). A table is made up of rows and columns. A row is also called a record (or tuple).

What are tuples and attributes?
An attribute value is an attribute name paired with an element of that attribute's domain, and a tuple is a set of attribute values in which no two distinct elements have the same name. Thus, in some accounts, a tuple is described as a function, mapping names to values.
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Components of DBMS

• Software-This is the set of programs used to control and manage the overall database. ...
• Hardware
• Data
• Procedures
• Database Access Language
• Query Processor
• Run Time Database Manager
• Data Manager

A database management system (DBMS) consists of several components. Each component plays very important role in the database management system environment. The major components of database management system are

Software

The main component of a DBMS is the software. It is the set of programs used to handle the database and to control and manage the overall computerized database

1. DBMS software itself, is the most important software component in the overall system
2. Operating system including network software being used in network, to share the data of database among multiple users.
3. Application programs developed in programming languages such as C++, Visual Basic that are used to to access database in database management system. Each program contains statements that request the DBMS to perform operation on database. The operations may include retrieving, updating, deleting data etc . The application program may be conventional or online  workstations or terminals.

Hardware

Hardware consists of a set of physical electronic devices such as computers (together with associated I/O devices like disk drives), storage devices, I/O channels, electromechanical devices that make interface between computers and the real world systems etc, and so on. It is impossible to implement the DBMS without the hardware devices, In a network, a powerful computer with high data processing speed and a storage device with large storage capacity is required as database server.

Data

Data is the most important component of the DBMS. The main purpose of DBMS is to process the data. In DBMS, databases are defined, constructed and then data is stored, updated and retrieved to and from the databases. The database contains both the actual (or operational) data and the metadata (data about data or description about data).

Procedures

Procedures refer to the instructions and rules that help to design the database and to use the DBMS. The users that operate and manage the DBMS require documented procedures on hot use or run the database management system. These may include.

1. Procedure to install the new DBMS.
2. To log on to the DBMS.
3. To use the DBMS or application program.
4. To make backup copies of database.
5. To change the structure of database.
6. To generate the reports of data retrieved from database..

Database Access Language

Data Access Language, or simply DAL, was a SQL-like language and application programming interface released by Apple Computer in 1990 to provide unified client/server access to database management systems.

Query Processor

Query Processing would mean the entire process or activity which involves querytranslation into low level instructions, queryoptimization to save resources, cost estimation or evaluation of query, and extraction of data from the database.

Run Time Database Manager

The runtime database stores user data such as session attributes and device fingerprints.

To manage the disk space usage of this database, you can clear some or all of its stored data.

To optimize performance or increase capacity, you can optionally deploy an external runtime database for the appliance.

Data Manager

Data management is the development and execution of architectures, policies, practices and procedures in order to manage the information lifecycle needs of an enterprise in an effective manner.

USERS-read  Database users for these four

Application Programmers-read above

Database Administrators-read above

End-Users-read above.
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Concepts of Schema

Schema- Design of a database is called the schema. Schema is of three types: Physical schema, logical schema and view schema

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-->A database schema is the skeleton structure that represents the logical view of the entire database. It defines how the data is organized and how the relations among them are associated. It formulates all the constraints that are to be applied on the data.

      concepts of schema

-->A database schema defines its entities and the relationship among them. It contains a descriptive detail of the database, which can be depicted by means of schema diagrams. It’s the database designers who design the schema to help programmers understand the database and make it useful.

A database schema can be divided  into two categories-

Physical Database Schema − This schema pertains to the actual storage of data and its form of storage like files, indices, etc. It defines how the data will be stored in a secondary storage.

Logical Database Schema − This schema defines all the logical constraints that need to be applied on the data stored. It defines tables, views, and integrity constraints.

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instance-The data stored in database at a particular moment of time is called instance of database.

--->A database instance is a set of memory structures that manage database files.       --->A database is a set of physical files on disk created by the Create  DATABASE statement. The instance manages its associated data and serves the users of the database.

                                   

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Data Independence

A database system normally contains a lot of data in addition to users’ data. For example, it stores data about data, known as metadata, to locate and retrieve data easily. It is rather difficult to modify or update a set of metadata once it is stored in the database. But as a DBMS expands, it needs to change over time to satisfy the requirements of the users. If the entire data is dependent, it would become a tedious and highly complex job.

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                         Data independence is the type of data transparency that matters for a centralised DBMS. It refers to the immunity of user applications to changes made in the definition and organization of data. Physical data independence deals with hiding the details of the storage structure from user applications. 
         
 

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SOME IMPORTANT CONCEPTS TO LEARN

What is a SQL database schema?

A schema is a collection of database objects (as far as this hour is concerned—tables) associated with one particular database username. This username is called the schema owner, or the owner of the related group of objects. You may have one or multiple schema's in a database.

What is a relational schema in database?

The term "schema" refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of relational databases). The formal definition of a database schema is a set of formulas (sentences) called integrity constraints imposed on a database.

What is a Sub schema?

A sub schema lets the user have access to different areas of applications in which the user designed. The areas that are included in an application are set, types, record types, data items, and data aggregates. Schema's may have many different sub schema''s that are all very different.

What is the physical design of a database?

During the physical design process, you convert the data gathered during the logical design phase into a description of the physical database, including tables and constraints. Physical design decisions, such as the type of index or partitioning have a large impact on query performance.

What is data abstraction in database management system?

This process of hiding irrelevant details from user is called data abstraction.You can get the complex data structure details at this level. Logical level: This is the middle level of 3-level data abstraction architecture. It describes what data is stored in database. View level: Highest level of data abstraction.

What is a schema in programming?

In computer programming, a schema (pronounced SKEE-mah) is the organization or structure for a database. The activity of data modeling leads to a schema. (The plural form is schemata. The term is from a Greek word for "form" or "figure."

What is a schema object in SQL?

A schema is a collection of logical structures of data, or schema objects. A schema is owned by a database user and has the same name as that user. Each user owns a single schema. Schema objects can be created and manipulated with SQL and include the following types of objects: Clusters.

What is logical and physical schema?

A logical data model or logical schema is a data model of a specific problem domain expressed independently of a particular database management product or storage technology (physical data model) but in terms of data structures such as relational tables and columns, object-oriented classes, or XML tags.
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DBMS Architecture

DBMS Architecture contains Schemas, Sub-schemas and Instances

Schemas:

The overall logical design of the database.

Sub-Schemas:

A sub schema is a subset of the schema and 

inherits the same property that a schema has. 

The plan (or scheme) for a view is often called 

sub-schemas.

Instances:

The collection of information stored in the

 database at a particular moment.

The difference between Schema and Instance are given in below table.

	Schema	Instance
Definition	The overall logical design of the database.	The collection of information stored in the database at a particular moment.
Includes	Table names,column names, datatypes, and size of columns, various constraint at logical level.	Actual data or information stored in tables in form of different records.
Change	changes infrequently.	changes frequently.
Cause of change	insertion of tables or columns and change in datatype,size or constraints on any column.	insert,delete or update operation on data stored in database.
Analogy	variable declaration	value of the variable