Assignment 1 - abeerafatima/learning-database GitHub Wiki

##Q1: What is data? Data is facts or information used usually to calculate,analyze or plane something. Data is collected and analyzed to create information suitable for making decisions. Data,information,knowledge and wisdom are closely related concepts.

##Q2: what is database? A database is a collection of information organization to provide efficient,retrieval. The collected information could be in any number or formates(electronic,printed,graphics,audio,statistical,combinations). There are physical and electronic database.

Q3: what is management system?

A management system is the framework of policies,processes and procedures used to ensure that an organization can fulfill all tasks required to achieve its objectives.

Q4: Advantages and disadvantages of DBMS?

** Advantages of DBMS:** The major advantages of DBMS are described below.

  1. Controlling Data Redundancy:
    In DBMS, all the data of an organization is integrated into a single database. The data is recorded at only one place in the database and it is not duplicated. In DBMS, the data redundancy can be controlled or reduced but is not removed completely. Sometimes, it is necessary to create duplicate copies of the same data items in order to relate tables with each other. By controlling the data redundancy, you can save storage space. Similarly, it is useful for retrieving data from database using queries.

  2. Data Consistency: By controlling the data redundancy, the data consistency is obtained. If a data item appears only once, any update to its value has to be performed only once and the updated value (new value of item) is immediately available to all users.

  3. Data Sharing: In DBMS, data can be shared by authorized users of the organization. The DBA manages the data and gives rights to users to access the data.

  4. Data Integration: In DBMS, data in database is stored in tables. A single database contains multiple tables and relationships can be created between tables (or associated data entities). This makes easy to retrieve and update data.

  5. Integrity Constraints: Integrity constraints or consistency rules can be applied to database so that the correct data can be entered into database. Example:The examples of integrity constraints are: (i) 'Issue Date' in a library system cannot be later than the corresponding 'Return Date' of a book. (ii) Maximum obtained marks in a subject cannot exceed 100. (iii) Registration number of BCS and MCS students must start with 'BCS' and 'MCS' respectively etc.

  6. Data Security:

              Data security is the protection of the database from unauthorized users. Only the authorized persons are allowed to access the database. Some of the users may be allowed to access only a part of database i.e., the data that is related to them or related to their department.

  7. Data Atomicity:

                A transaction in commercial databases is referred to as atomic unit of work. For example, when you purchase something from a point of sale (POS) terminal, a number of tasks are performed such as;

Company stock is updated. Amount is added in company's account. Sales person's commission increases etc. 8. Database Access Language:

                         Most of the DBMSs provide SQL as standard database access language. It is used to access data from multiple tables of a database.

  1. Development of Application:

                            The cost and time for developing new applications is also reduced. The DBMS provides tools that can be used to develop application programs. For example, some wizards are available to generate Forms and Reports. Stored procedures (stored on server side) also reduce the size of application

programs. 10. Creating Forms:

               Form is very important object of DBMS. You can create Forms very easily and quickly in DBMS, Once a Form is created, it can be used many times and it can be modified very easily. The created Forms are also saved along with database and behave like a software component.

Disadvantages of Database Management System (DBMS):

Although there are many advantages but 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 files. It is difficult and time consuming method to convert data of data files into database. You have to hire DBA (or database designer) and system designer along with application programmers; Alternatively, you have to take the services of some software houses. So a lot of money has to be paid for developing database and related software.

  3. Cost of Staff Training:

                       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 pay a lot of amount on the training of staff to run the DBMS.

  4. Appointing Technical Staff:

                           The trained technical persons such as database administrator and application programmers etc are required to handle the DBMS. You have to pay handsome salaries to these persons. Therefore, the system cost increases.

  5. Database Failures: In most of the organizations, all data is integrated into a single database. If database is corrupted due to power failure or it is corrupted on the storage media, then our valuable data may be lost or whole system stops.

Q5: Types of database management system?

1: Hierarchical database 2: Network database 3: Relational database 4: Object-oriented database

HIERARCHICAL DATABASE:

A DBMS is said to be hierarchical if the relationships among data in the database are established in such a way that one data item is present as the subordinate of another one. Here subordinate means that items have parent- child relationships among them. Direct relationships exist between any two records that are stored consecutively.

NETWORK DATABASE:

A DBMS is said to be a Network DBMS if the relationships among data in the database are of type many-to-many. The relationships among many-to-many appears in the form of a network. ##RELATIONAL DATABASE: A DBMS is said to be a Relational DBMS or RDBMS if the database relationships are treated in the form of a table. there are three keys on relational DBMS 1)relation 2)domain 3)attributes ##OBJECT-ORIENTED DATABASE: Object-oriented databases use small, reusable chunks of software called objects. The objects themselves are stored in the object-oriented database. Each object consists of two elements: First, they are more costly to develop. Second, most organizations are reluctant to abandon or convert from those databases that they have already invested money in developing and implementing. However, the benefits to object-oriented databases are compelling. The ability to mix and match reusable objects provides incredible multimedia capability.