Database and Database Management Systems.

Objectives:

• What is the difference between data and information?

• What is Database?

• What is a Database Management System(DBMS)?

• What are the roles and advantages of DBMS?

• What are the different type of DBMS?

What is the difference between data and information?

Data are raw facts. Raw fact => a fact which have not yet been processed to reveal their meaning.
Information is the result of processing raw data to reveal its meaning.

What is Database? 

A Database is a collection of information that is similar in nature.
A telephone book, a list of your students, and an inventory list are all examples of a database.

What is a Database Management System?

A database management system (DBMS) is a collection of programs that manages the database structure and controls access to the data stored in the database.

What are the roles and advantages of DBMS?

The DBMS serves as the intermediary between the user and the database.

The database structure itself is stored as a collection of files, and the only way to access the data in those files is through the DBMS.

The DBMS receives all application requests and translates them into the complex operations required to fulfill those requests.

The DBMS hides much of the database’s internal complexity from the application programs and users.

The DBMS helps make data management more efficient and effective. In particular, a DBMS provides advantages such as:

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

1. 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.

1. 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.

1. 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 $45.95 and its national sales office shows the same product’s price as $43.95. The probability of data inconsistency is greatly reduced in a properly designed database.

1. 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. 

1. Improved decision making. Better-managed data and improved data access make it possible to generate better quality information, on which better decisions are based.

1. 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. 

What are the different type of DBMS?

There are 4 main types of Database Management System (DBMS) and these are based upon their management of database structures.

In simple words, the types of DBMS are entirely dependent upon how the database is structured by that particular DBMS.

The 4 main types of DBMS are:

• Hierarchical DBMS

• Network DBMS

• Relational DBMS

• Object-oriented Databases (OODBMS)

1)  Hierarchical DBMS : 

• One of the oldest methods of organizing and storing data,still used by some organizations for making travel reservation.Principally used on mainframe computers.

• The database is organized in pyramid fashion, like the branches of a tree extending downwards.

• Related fields or records are grouped together so that there are higher-level records and lower-level records, just like the parents in a family tree sit above the subordinated children. 

• The parent record at the top of the pyramid is called the root record.

• A child record always has only one parent record to which it is linked. In contrast, a parent record may have more than one child record linked to it.

• Hierarchical databases work by moving from the top down. A record search is conducted by starting at the top of the pyramid and working down through the tree from parent to child until the appropriate child record is found. Furthermore, each child can also be a parent with children underneath it. 

• Advantage : Can be accessed and updated rapidly because the tree-like structure and the relationships between records are defined in advance. 

• Disadvantage : Each child in the tree may have only one parent, and relationships or linkages between children are not permitted, even if they make sense from a logical standpoint. Hierarchical databases are so rigid in their design that adding a new field or record requires that the entire database be redefined.

2)  Network DBMS

• Similar to hierarchical databases by also having a hierarchical structure.

• Key differences from hierarchical  databases:

• Instead of looking like an upside-down tree, a network database looks more like a cobweb or interconnected network of records. 

• In network databases, children are called members and parents are called owners.

• The most important difference is that each child or member can have more than one parent (or owner).  

• Like hierarchical databases, network databases are principally used on mainframe computers. Since more connections can be made between different types of data, network databases are considered more flexible.

• Limitations: 

• Network databases must be defined in advance.

• There is also a limit to the number of connections that can be made between records. 

 3) Relational DBMS

  

 

• The relationship between data files is relational, not hierarchical.

• Relational databases connect data in different files by using common data elements or a key field, unlike hierarchical and network databases require the user to pass down through a hierarchy in order to access needed data.  

• Data in relational databases is stored in different tables, each having a key field that uniquely identifies each row.

• Relational databases are more flexible than either the hierarchical or network database structures.

• In relational databases, tables or files filled with data are called relations, tuples designates a row or record, and columns are referred to as attributes or fields. 

• Relational databases work on the principle that each table has a key field that uniquely identifies each row, and that these key fields can be used to connect one table of data to another.

• The relational database has become quite popular for two major reasons.

•  First, relational databases can be used with little or no training. 

•  Second, database entries can be modified without redefining the entire structure.

•  The downside of using a relational database is that searching for data can take more time than if other methods are used. 

4) Object-oriented Databases (OODBMS)

• Able to handle many new data types, including graphics, photographs, audio, and video.

• 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: 1) a piece of data (e.g., sound, video, text, or graphics), and 2) the instructions, or software programs called methods, for what to do with the data.

• Disadvantages :

• 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.

• Benefits  The ability to mix and match reusable objects provides incredible multimedia capability. Healthcare organizations, for example, can store, track, and recall CAT scans, X-rays, electrocardiograms and many other forms of crucial data.