Dear Aspirant,
As you know Computer is very important section to get a good score for Bank Exam 2016.Today we are covering the study material on Database Management System,that will help you succeed in the upcoming exam for Bank.
Database: A database contains a collection of related items or facts arranged in a specific structure.
DBMS: DBMS is the acronym of Database Management System.It is a collection of interrelated data and a set of programs to access this data in a convenient and efficient way. It controls the organization, storage, retrieval, security and integrity of data in a database.
The information contained in a database is represented on two levels:
- Data (which is large and is being frequently modified)
- Structure of data (which is small and stable in time)
Features of Database
- Faithfulness: The design and implementation should be faithful to the requirements.
- Avoid Redundancy: This value is important because redundancy.
- Simplicity: Simplicity requires that the design and implementation avoid introducing more elements than are absolutely necessary.
- Right kind of element: Attributes are easier to implement but entity sets are relationships are necessary to ensure that the right kind of element is introduced.
Types of Database:
- Centralized Database: All data is located at a single site.
- Distributed Database: The database is stored on several computer.
- Management of information
- Liaison with users
- Enforcing security and integrity rules
- Database backup and recovery
- Monitoring database performance
Database designers:
- Person responsible for preparing external schemas for applications, identifying and integrating user needs into a conceptual (or community or enterprise) schema.
Application programmers:
- Application programmers write programs to access/insert/update/delete data from/to database by making use of the various database components.
End users:
- Users who query and update the database through fixed programs (invoked by non-programmer users) e.g., banking.
- Data independence
- Reduced data redundancy
- Increased security
- Better flexibility
- Effective data sharing
- Enforces integrity constraints
- Enables backup and recovery
Most important term about database:
Fields:- Each piece of information in the address book is stored in its own location called a field.
Records:- One full set of fields that is all the related information about one person or object is called a record.
Tables:- A complete colleciton of records makes a table.
Levels of Data Abstraction: There are three levels of data abstraction as given below
- Physical Level: It is lowest level of abstraction and describes how the data are actually stored and complex low level data structures in detail.
- Logical Level: It is the next higher level of abstraction and describes what data are stored and what relationships exist among those data. At the logical level, each such record is described by a type definition and the interrelationship of these record types is defined as well. Database administrators usually work at this level of abstraction.
- View Level: It is the highest level of abstraction and describes only part of the entire database and hides the details of the logical level.
View Level …Defined by User
Difference between File system & DBMS
File System
- File system is a collection of data. Any management with the file system, user has to write the procedures
- File system gives the details of the data representation and Storage of data.
- In File system storing and retrieving of data cannot be done efficiently.
- Concurrent access to the data in the file system has many problems like reading the file while other deleting some information, updating some information
- File system doesn’t provide crash recovery mechanism.eg. While we are entering some data into the file if System crashes then content of the file is lost.
- Protecting a file under file system is very difficult.
DBMS
- It is a collection of data and user is not required to write the procedures for managing the database.
- DBMS provides an abstract view of data that hides the details.
- It is efficient to use since there are wide varieties of sophisticated techniques to store and retrieve the data.
- It takes care of Concurrent access using some form of locking.
- DBMS has crash recovery mechanism, DBMS protects user from the effects of system failures.
- DBMS has a good protection mechanism.
Working with a Database:
The DBMS interface presents the user with data and the tools required to work with the data.
- Creating tables: The first step in building any database is to create one or more tables. As we know tables hold the raw data that the DBMS will work with.
- Entering and editing data: It allows you to create or edit a data entry form.
- viewing data: The way data appears on screen contributes to how well users can work with it.
- Querying the database: A query is a more powerful type of filter that can gather information from multiple tables in a relational database.
- Sorting records: Sorting arranges records according to the contents of one or more fields.
- Generating reports: A report is printed information that, like a query result, is assembled by gathering data based on user supplied criteria.
Types of Schemas: It can be classified into three parts, according to the levels of abstraction.
- Physical/Internal Schema: Describes the database design at the physical level.
- Logical/Conceptual Schema/Community User View: Describes the database design at the logical level.
- Sub-schemas /View/External Schema: Describes different views of the database views may be queried combined in queries with base relations, used to define other views in general not updated freely.
Thanks.
Gradeup..
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