04. Data, Metadata, Information, Models, RDBMS, ER-Models

What is Data Actually?

Data:
 It is Stored Representation of OBJECTS and EVENTS That have Meaning and Importance in the user's Environment. Data can be Structure OR Unstructured.

• Structured ------- No., Name, Address, DOB, .....
• Unstructured ---- Photos, Videos, AddrMap,.......

What is Information Actually?

Information:

 It is Data that is in Processed Form, such that it increases the Knowledge of the person who uses the data.

What is Metadata Actually?

Metadata:

 It is the data which describes the properties OR Characteristics of End users data and the context of the data.
 Metadata Properties can include information such as:

• Data Name
• Definitions
• Length OR Size
• Values Allowed
• Source of Data
• Ownership

Metadata and Data are always separate.
Metadata enables the database designers and programmer to understand exactly in which from the data should exist with in the system.

Database Management Systems:
 Database Management Systems is software that is used to Create, Maintain, and Provide Controlled Access to user Databases.
Database Management Systems Should Provide Systematic Method of

• Creating the Database
• Updating the Dtabase
• Storing the Database
• Retrieving of Database

Database Management System Evolution

• First time introduced during 1960's
• Relational Model First Defined by E.F Codd (IBM) in 1970

Objectives Behind Evolution....

• Provide Greater Independence Between Programs and Data
• Reduce the maintenance cost of software
• Mange complex data types and structures
• Provide easier and faster access to data even for novice users
• Provide future sensation for powerful platforms for decision support systems and expert systems

Expected Features of DBMS Software

• Enable end users and application programmers to share the data
• Enable Data shared among multiple applications
• Should not propagate and store data in new files for every new application
• Should provide facility for....

1. Controlling Data Access
2. Enforce Data Integrity
3. Manage Concurrency Control
4. Restoring the Data in system failures

Different Database Models

• Flat File DBMS
• Hierarchical DBMS
• Network DBMS
• Relational DBMS
• Object-Oriented DBMS
• Object-Relational DBMS
• Data Warehousing
• Web-Enabled DBMS

The Database Application Activities Include....

• Create ---- Add new data to database.
• Read ------ Read current Database data
• Update --- Updata OR modify current database data
• Delete --- Delete current data from the database

The Different Tables Supported by Oracle Database are.....

• Relational Tables
• Object Relational Tables
• Index Organized Tables
• External Tables
• Partitioned Views
• Materialized Views
• Temporary Tables
• Clustered Tables
• Dropped Tables

General Facts about Relational Model

The Model was first outlined by Dr. E. F. Codd in 1970.

The Component of the Model are...

• Collection of Objects OR Relations that Store the Data
• A set of Operators that can act on the Relations to Produce Other Relations
• Data Integrity for Accuracy and Consistency
• A Relational Database should use relations or two dimensional tables to store Information

Data Models:

Data Models help in exploring ideas and improve the understanding of the database design FOR both developers and system designers

Purpose of Data Models:

• Communicate
• Categorize
• Describe
• Specify
• Investigate
• Evolve
• Analyze
• Imitate

Relational Database (RDBMS) Properties:

• Should be accessed and modified by executing STRUCTURED QUERY LANGUAGE (SQL) Statements only
• Should Contain a collection of tables with no physical pointers
• Should use a set of Operators
• Need not specify the access route to the tables and data
• There is no need to identify how the data is arranged physically

How to communicate with RDBMS?

• The structured query language is used to communicate with RDBMS

Relational Database Terminology:

ROW (or) TUPLE: 

• It Represents all data required for a particular instance in an entity.
• Each Row in an Entity is Uniquely Identified by declaring it as PRIMARY KEY OR UNIQUE.
• The order of the Rows is not Significant, while retrieving the data.

COLUMN (or) ATTRIBUTE:

• It represents one kind of data in a table vertically collected.
• The column order is not significant when storing the data.

FIELD:

• It can be found at the intersection of a Row and a Column.
• A field can have only one value, or may not have a value at all
• The Absence of value in Oracle is represented as NULL.

ER-Model:

• It documents information for the organization in a clear, precise format
• Provides a clear picture of the scope of the information requirement
• Provides an easily understood pictorial map for the database design
• It offers an effective framework FOR integrating Multiple applications

Key Components in ER-Model:

• Entity: It is a thing of significance about which the information need to be known.
• Attributes: It is something that describes OR Qualifies an entity. Each attribute may be mandatory OR optional.
• Relation: It is any rule OR situation that should be satisfied between the attribute AND attributes of an Entity OR Entities.