(i) σ
(ii) π
(iii) U
(iv) ∩
(v) -
(vi) X

(i) Relational Algebra, was first created by Edgar F Codd while at IBM. It was used for modeling the data stored in relational databases and defining queries on it.
(ii) Relational Algebra is a procedural query language used to query the database tables using SQL.
(iii) Relational algebra operations are performed recursively on a relation (table) to yield an output. The output of these operations is a new relation, which might be formed by one or more input relations.

(i) Database Administrators(DBA)
(ii) Application or software developers
(iii) End User
(iv) Database designers

Entity Relationship Model (ER model):
(i) In this database mo-ad., relationship are created by dividing the object into entity and its characteristics into attributes.
(ii) It was developed by Chen in 1976. This model is useful in developing a conceptual design for the database.
(iii) It is very simple and easy to design logical view of data. The developer can easily understand the system by looking at ER model constructed.

(i) Hierarchical model was developed by IBM as Information Management System.
(ii) In Hierarchical model, data is represented as a simple tree like structure form. This model represents a one-to-many relationship ie parent-child relationship.
(iii) One child can have only one parent but one parent can have many children. This model is mainly used in IBM Main Frame computers.

(i) The Relational Database model was first proposed by E.P. Codd in 1970. It is the most widespread data model used for database applications around the world.
(ii) The basic structure of data in relational model is tables (relations). All the information's related to a particular type is stored in rows of that table.
(iii) Hence tables are also known as relations in a relational model. A relation key is an attribute which uniquely identifies a particular tuple (row in a relation (tabler).

The different types of a Data Model
(i) Hierarchical Model
(ii) Relational Model
(iii) Network Database Model
(iv) Entity Relationship Model
(v) Object Model

(i) A data model describes how the data can be represented and accessed from a software after complete implementation
(ii) It is a simple abstraction of complex real world data gathering environment.
(iii) The main purpose of data model is to give an idea as how the final system or software will look like after development is completed.

(i) RDBMS
(ii) DBMS
(iii) RDBMS
(iv) DBMS

(i) Relation
(ii) Tuple
(iii) Attribute

(i) Table is the entire collection of related data in one table, referred to as a File or Table where the data is organized as row and column.
(ii) Each row in a table represents a record, which is a set of data for each database entry.
(iii) Each table column represents a Field, which groups each piece or item of data among the records into specific categories or types of data. Eg. StuNo., StuName, StuAge, StuClass, StuSec.,
A Table is known as a RELATIQN
A Row is known as a TUPLE
A column is known as an ATTRIBUTE

The Database Management System can be divided into five major components as follows:
(i) Hardware
(ii) Software
(iii) Data
(iv) Procedures / Methods
(v) Database Access Languages

Advantages of DBMS:
(i) Segregation of application program
(ii) Minimal data duplication or Data Redundancy
(iii) Easy retrieval of data using the Query Language
(iv) Reduced development time and maintenance

(i) A DBMS is a soft ware that allows us to create, define and manipulate database, allowing users to store, process and analyze data easily.
(ii) DBMS provides us with an interface or a tool, to perform various operations to create a database, storing of data and for updating data, etc.
(iii) DBMS also provides protection and security to the databases. It also maintains data consistency in case of multiple users.

(i) A database is an organized collection of data, generally stored and accessed electronically from a computer system.
(ii) The term "database" is also used to refer to any of the DBMS, the database system or an application associated with the database
(iii) Because of the close relationship between them, the term "database" is often used casually to refer to both a database and the DBMS used to manipulate it.