FUNDAMENTALS OF DATABASE MANAGEMENT SYSTEM

We often hear the word data in our daily life. It can be anything like any number, the name of a place or name of person etc.

Some common examples of data are prices, employee’s names, phone numbers, quantity etc.

Data can be defined as a collection of raw facts that can be stored and processed by a computer or by a human being.

These data items can be processed and analysed to draw meaningful conclusions.

Information is data that has been converted into more intelligent and useful form, it is helpful for decision making e.g. Inventory reports, Comparison of sales figures, marks lists, report card etc.

So, we see that the information is obtained when we assemble and arrange the data into meaningful form.

Difference between Data and Information:

Data And Information:

Data

Information

Data is row facts and figures.

Information is organised form of facts and figures.

Data is not significant for decision.

Information is of utmost significance for decision making.

Database:

An unorganised data has no meaning to the organisation.

Increased demand of data is being felt now days in every type of business may be Banks, Railways, Telephone companies or any other. What is important to store data in an organised way.

When related information is kept in an organised way, it becomes Database e.g. the case of dictionary or telephone directory or employee’s information.

There are many operations that we can perform on a database. These are:-

§  Adding new information

§  Retrieving the required information.

§  Modifying the existing information.

§  Sorting the information in ascending/ descending order.


Characterstics of Data in a Database:

The data in a database should have the following features characteristics:

§  Consistency: When more than one data element represents real world values, the values should consistent with respect to the relationship. The copies of same data in different files must contain the same information.

§  Reduced Redudancy:The data items in a database must not contain the duplicated records/ same data. Some level of redundancy is allowed but as far as possible, duplication of data is not there.

§  Easy of work: DBMS provides interfaces which are very easy to work. The language syntax is very easy, it is usually simple English which is learnt easily.

§  User Interface: DBMS provides the user with good user inter- face, it provides flexibility and good working environment for the programmer and the user.

§  Shared Data: Data in database is shared among many different users and applications; it is kept as a central repository.

§  Security: Data is protected from unauthorised access; unauthorised persons are not allowed to access the data.

§  Independence: Data at different levels should be independent of hardware or access strategy, changes in one level should not affect the other level.

§  Backup: Database provides backup and recovery procedure which restores the database to a correct state when a failure occurs due to hardware and software errors.


Components of Database System:

A database system is composed of five major components. These are:

§  Data is the basis for any activity in the organisation. DBMS works with the management of data. It is the core of any organisation and its functionality.

§  Hardware consists of the CPU all other peripheral devices (I/O and storage devices) hardware machines and memory. Proper care is taken to select hardware required for the efficient working of DBMS.

§  Software includes both the system software and other supporting application software, which are used to work on the database.

§  Procedures refer to the rules and instructions that govern the design and use of the database. Procedures generally include instructions like how to log on to DBMS, how to run application programs, etc.

§  Users those persons who need access and retrieve the information from the database using interfaces. This component includes all type of users like naive users, online users, application programmers and database administrates.


Database Languages:

To carry out the functions of DBMS in an efficient manner, DBMS uses data language, which is usually a combination of sub languages like DDL, DML, and DCL.

§  DDL: DDL is acronym for Data Definition Language. It is used for defining the data storage structures and formats. Data objects which are a part of database are created using DDL. All data objects can be created altered and deleted using DDL.

§  DML: DML is acronym for Data Manipulation Language. This language enables users to access or manipulate (retrieve, insert, delete update) data as organised by certain data models.

§  DCL: DCL is acronym for Data Control Language. It is used to implement security schemes on to the data. By controlling the access to data. DCL is used to give and take back the permissions on data.

Thus DDL, DML, and DCL together form a data language to work with a database.


Advantages of DBMS :

DBMS has many advantages, which are listed below:

§  Control Redundancy: DBMS controls the unnecessary duplication of same data in different files. Redundancy cannot be eliminated altogether, it can be reduced, thus controlled redundancy is the very fast advantage.

§  Data Sharing: Some data which is stored as central repository can be used by multiple users simultaneously. The users need not create their own files for that data which is already there.

§  Inconsistency Elimination: Data is said to be inconsistent if two entries of the same data do not match. Inconsistency is eliminated in centralised system because changes to the data are done only at one place.

§  Better Service: In Case of centralised database, users have access to the recent information; they can have better service because response to requests is fast.

§  Flexibility in the system: Changes are made easily in a centralised database, thus flexibility of the system is improved.

§  Enforcement of standards: Since database is centralised, standards can be enforced easily at the required level like departmental, company level or other high levels.

§  Improved Integrity: Here data is centralised, it is said to be accessed by many users at one time, and integrity constraints are to be enforced. Integrity is improved in DBMS.

§  Reduced Cost: Although initial cost of setting up a database is higher, it is easier to respond to unanticipated requests and queries. The overall cost of developing DBMS is reduced.

§  Restricting Unauthorised Access: DBMS provides security and authorised systems, DBMS controls unauthorised access through different checks which enables only authorised users can have access to the data., So, Security is also maintained.


Disadvantages of DBMS :

DBMS has many advantages as well as disadvantages, which are listed below:

§  Higher Cost: Cost of using DBMS is high because new hardware is to be procured; cost of migrating the data from traditional system to DBMS is quite high.

§  Size: DBMS is extremely large piece of software, it occupies many MBs of disk space and also requires huge amount of memory to run efficiently.

§  Confidentially and Security Reduction: When data is centralised, it is easily accessible to users from remote locations, thus possibility of destruction of data is there. Various measures are taken to reduce the chances of unauthorised access.

§  Increased Complexity: DBMS is extremely complex software. Database designers, developers and administrators have to take full advantage of it.

§  Reduced Data Quality: Adequate controls are needed to control data quality because data is handled by users who are updating the data.

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