Grade 12 - Database Management System (DBMS)

1.1 Introduction to Data, Database, DBMS

Data: Raw facts or figures that on their own have no meaning, such as numbers, names, or dates.

Database: A structured collection of related data stored in a way that makes it easy to retrieve, manage, and update.

DBMS (Database Management System): Software that helps users create, access, manage, and update databases. It acts as an interface between the database and the user.DBMS is a computerized record keeping system. It is a software that defines, manipulates and manage the database. It allows to access the file, update the record and retrieve data as requested. In other word, DBMS is defined as the collection of interrelated data and set of programs to access there data. The collection of data is usually a database which contains the information about any particular organization. The primary goal of DBMS is to provide an effective and efficient environment for both data retrieval and storing data in database. For example MS Access, Oracle, MY SQL, Fox-Pro, D-base etc

Examples of DBMS: MySQL, Oracle, MS SQL Server, PostgreSQL.

1.2 Fields, Records, Keys and Objects

Field: It holds single facts or attribute to an entity, a single piece of data in a database, such as a student's name or ID. In a table, it represents a column.

Record: A complete set of related fields, such as all the information about one student. It represents a row in a table.

Object: Any database element such as a table, view, index, or stored procedure. Objects store or interact with data.

Types of Keys

Primary Key: A field (or combination) that uniquely identifies each record in a table.Although several candidate key may exist,one of the candidate keys is selected to be the primary key

Candidate Key: A field or set of fields that can qualify as a unique key. One of these is chosen as the primary key.

Alternate Key: Candidate keys that are not selected as the primary key.

1.3 Advantages of Using DBMS

• Data Integrity: Ensures accuracy and consistency of data.
• Data Security: Access to data can be controlled using user permissions.
• Data Sharing: Multiple users can access the same data simultaneously.
• Backup and Recovery: DBMS can automatically back up data and recover it in case of failures.
• Reduced Data Redundancy: It prevents duplicate data using normalization and table relationships.
• Concurrent data access: Data can be shared easily among several users.

1.4 DDL and DML

DDL (Data Definition Language): 1)DDL is used by the database designer and programmers to specify the content and the structure of table. It is used to define the physical characteristics of record. It includes commands that manipulate the structure of object such as tables: For eg, to create table Syntax: CREATE TABLE table_name (field_name1 data_type1 field_name2 data_type2 ………); CREATE TABLE Student (SN Number Fname text);

Examples: CREATE, ALTER, DROP

DML (Data Manipulation Language): DML is related with manipulation of records such as retrieval, sorting, display and deletion of records or data. It helps user to use query and display report of the table. It provide technique for processing the database. It includes commands like insert, delete, select, and update to manipulate the information stored in the database. Syntax: INSERT INTO table_name VALUES (list of values); INSERT INTO student VALUES (1 RAM);

Examples: SELECT, INSERT, UPDATE, DELETE

1.5 Types of Database Models

1. Hierarchical Model

It is one of the oldest type of database model. In this model data are represented in the forms of record, each record has multiple field or attributes. All records are arranged in database as tree like structure. The relationship between the records is called parent child relationship in which one child record relates to only a single parent i.e child posses property only property of a single parent. Here child are restricted to use the property of a parent to whom it doesn't belong.

Advantages:

• It is the simplest and the easiest model
• It supports one to one or one to many relationship.
• Searching is easier and faster if parent is known

Disdvantages:

• It is an old fashion and outdated database model.
• It doesn’t support many to one relationship.
• It doesn’t reduce data redundancy because some data are written over different places.

2. Network Model

This network model replace hierarchical model due to some limitation on the model. Suppose an employee relates to two different department then hierarchical model cannot be able to arrange record in proper place. So, network database model was emerged to arrange non-hierarchical database. The structure of database is more like graph rather than tree structure. A network model consists of collection of record which are interrelated to each other with the help of relationship. Each records have multiple fields and each field has only one data value. In this type of model a parent may have multiple child, as well as child can have multiple parent.Similar to the hierarchical model but allows many-to-many relationships. Records are connected as nodes in a graph.

Advantages:

• It accepts many to many relationships. So, It is more flexible .
• It reduces data redundancy.
• This network mode is simple and easy to design.
• Searching is faster due to use of multi-directional pointer.

Disdvantages:

• Needs long program to handle the relationship.
• Lack of structural independence.
• Less security

3. Relational Model

In relational database model, the data are organized into tables which contains multiple row and columns. These tables are called relations. A row in a table represents a relationship among a set of values. Since, a table is collection of such relationship. It is generally referred to the mathematical term relations from which the relational database model derives its name. It is also known as RDBMS. Note: The database system which stores and display data in tabular format of rows and column like spreadsheet is known as RDBMS. It is the most practical DBMS those days. For example, MS-Access, MY SQL, Oracle etcData is stored in tables (relations), and relationships between tables are maintained through keys.

Advantages:

• There is less data redundancy.
• Breaking of complex database into simple is very much easier.
• Database processing is faster than other model.

Disdvantages:

• Establishing more relationships complex.
• It requires powerful computer and data storage device.

1.6 Normalization

Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity.The process of breaking down or decomposing as complex relation into simple relation. It reduces redundancy (unnecessary repetition of data) using principle of non-loss decomposition in which table are reduce to smaller tables without loss of information. Normalization is the database design process in which complex database table is broken down into simple separate tables. It makes data model more flexible and easier to maintain.EF Codd has introduced few rules for normalizing the database in 1970 and these rules are known as normal forms. This process minimizes and controls the duplication of data in a database and also provides a rapid search for data from database.

First Normal Form (1NF)

1NF sets the very basic rules for on organized database. It eliminates duplicate columns from the same table. It creates separate tables from each group of related data and identify each row with a unique column called primary key. The objective of 1NF is to divide the base datas into logical units called tables.It removes repeating groups and ensures that each field contains only atomic (indivisible) values.

Second Normal Form (2NF)

It further addresses the concept of remaining duplicate data. It should be in first normal form. It removes the date that applies to multiple row of a table and place them in separate tables. The objective of second NF is to take data i.e. partly dependent upon the primary key and enter the data into another table.It eemoves partial dependencies — every non-key attribute should depend on the whole primary key.

Third Normal Form (3NF)

It should be in second normal form. It removes the column that are not dependent on primary key using 3NF.It removes transitive dependencies — non-key attributes should not depend on other non-key attributes.

1.7 Centralized vs Distributed Databases

1.8 Database Security

Database security protects data from unauthorized access, corruption, or loss.

Key Security Features:

• Authentication: Confirms user identity before granting access.
• Authorization: Determines what actions users are allowed to perform.
• Encryption: Encodes data to prevent unauthorized access.
• Backup: Regular backups protect against data loss.
• Audit Trails: Tracks who accessed or modified data and when.

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