O LEVEL- IT TOOLS & BUSINESS SYSTEM

TRICKS TO CRACK FIRST PAPER:   

                            M1-R4: IT TOOLS & BUSINESS SYSTEMS

     

        SOME IMPORTANT TOPICS WHICH FREQUENTLY ASKED EVERY            YEAR:--

DATABASE MANAGEMENT SYSTEM (DBMS)--

Database is a collection of related data and data is a collection of facts and figures that can be processed to produce information. Mostly data represents recordable facts. Data aids in producing information, which is based on facts. For example, if we have data about marks obtained by all students, we can then conclude about toppers and average marks.

 A database management system stores data in such a way that it becomes easier to retrieve, manipulate, and produce information.

 Characteristics

Traditionally, data was organized in file formats. DBMS was a new concept then, and all the research was done to make it overcome the deficiencies in traditional style of data management. A modern DBMS has the following characteristics:  

Real-world entity: A modern DBMS is more realistic and uses real-world· entities to design its architecture. It uses the behavior and attributes too. For example, a school database may use students as an entity and their age as an attribute.  

Relation-based tables: DBMS allows entities and relations among them to· form tables. A user can understand the architecture of a database just by looking at the table names.  

Isolation of data and application: A database system is entirely different· than its data. A database is an active entity, whereas data is said to be passive, on which the database works and organizes. DBMS also stores metadata, which is data about data, to ease its own process.

 Less redundancy: DBMS follows the rules of normalization, which splits a· relation when any of its attributes is having redundancy in values. Normalization is a mathematically rich and scientific process that reduces data redundancy.

 Consistency: Consistency is a state where every relation in a database· remains consistent. There exist methods and techniques, which can detect attempt of leaving database in inconsistent state. A DBMS can provide greater  consistency as compared to earlier forms of data storing applications like fileprocessing systems.

 Query Language: DBMS is equipped with query language, which makes it· more efficient to retrieve and manipulate data. A user can apply as many and as different filtering options as required to retrieve a set of data. Traditionally it was not possible where file-processing system was used.

 Multiuser and Concurrent Access: DBMS supports multi-user environment· and allows them to access and manipulate data in parallel. Though there are restrictions on transactions when users attempt to handle the same data item, but users are always unaware of them.  Multiple views: DBMS offers multiple views for different users. A user who is· in the Sales department will have a different view of database than a person working in the Production department. This feature enables the users to have a concentrate view of the database according to their requirements.  

Security: Features like multiple views offer security to some extent where· users are unable to access data of other users and departments. DBMS offers methods to impose constraints while entering data into the database and retrieving the same at a later stage. DBMS offers many different levels of security features, which enables multiple users to have different views with different features. For example, a user in the Sales department cannot see the data that belongs to the Purchase department. Additionally, it can also be managed how much data of the Sales department should be displayed to the user. Since a DBMS is not saved on the disk as traditional file systems, it is very hard for miscreants to break the code.

SQL AND RDMS--

SQL is a language to operate databases; it includes database creation, deletion, fetching rows, modifying rows, etc. SQL is an ANSI (American National Standards Institute) standard language, but there are many different versions of the SQL language.

 What is SQL?

 SQL is Structured Query Language, which is a computer language for storing, manipulating and retrieving data stored in a relational database. SQL is the standard language for Relational Database System. All the Relational Database Management Systems (RDMS) like MySQL, MS Access, Oracle, Sybase, Informix, Postgres and SQL Server use SQL as their standard database language. Also, they are using different dialects, such as:  MS SQL Server using T-SQL,·  Oracle using PL/SQL,·  MS Access version of SQL is called JET SQL (native format) etc.·

 Why SQL?

 SQL is widely popular because it offers the following advantages:  Allows users to access data in the relational database management systems.·  Allows users to describe the data.·  Allows users to define the data in a database and manipulate that data.·  Allows to embed within other languages using SQL modules, libraries· & pre-compilers.  Allows users to create and drop databases and tables.·  Allows users to create view, stored procedure, functions in a database.·  Allows users to set permissions on tables, procedures and views.·

SQL Process When you are executing an SQL command for any RDBMS, the system determines the best way to carry out your request and SQL engine figures out how to interpret the task. There are various components included in this process. These components are –  Query Dispatcher·  Optimization Engines·  Classic Query Engine·  SQL Query Engine, etc.· A classic query engine handles all the non-SQL queries, but a SQL query engine won't handle logical files.

Following is a simple diagram showing the SQL Architecture:

What is RDBMS?

 RDBMS stands for Relational Database Management System. 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 a table?

The data in an RDBMS is stored in database objects which are called as tables. This table is basically a collection of related data entries and it consists of numerous columns and rows. Remember, a table is the most common and simplest form of data storage in a relational database. The following program is an example of a CUSTOMERS table:

 What is a field?

Every table is broken up into smaller entities called fields. The fields in the CUSTOMERS table consist of ID, NAME, AGE, ADDRESS and SALARY. A field is a column in a table that is designed to maintain specific information about every record in the table.

What is a Record or a Row?

 A record is also called as a row of data is each individual entry that exists in a table. For example, there are 6 records in the above CUSTOMERS table.