SS2 First Term Data Processing Lesson Note – Relational Model

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WEEK SEVEN:

WEEK EIGHT                                                                       

TOPIC:  RELATIONAL MODEL

CONTENT: 

1. Creating and modifying relations using SQL
2. Integrity constraints over relations

Sub-topic 1

The relational model for database management is a database model based on first –order predicate logic, first formulated and proposed in 1969 by E.F. Codd.

The purpose of the relational model is to provide a declarative method for specifying data and queries.

Creating and modifying relations using SQL

Creating and modifying relations simply is the process of creating and modifying a database. Data-definition queries can be very convenient. You can regularly delete and re-create parts of your database schema merely by running some queries. Consider using a data-definition query if you are familiar with SQL statements and you plan to delete and re-create particular tables, constraints, indexes or relationships.

A relation is a table structure definition (set of column definitions) along with the data appearing in that structure. The structure definition is the heading and the data appearing in it is the body, a set of rows. A database relvar (relation variable) is commonly known as base table. Operators called the Update operators are used to interact with the database. Example, INSERT, UPDATE or DELETE.

SQL

SQL (often referred to as structured query language) is a programming language designed for managing data in relational database management system (RDBMS) it is use for data insert, query, update and delete, schema creation and modification, and data access control. SQL can achieve the following in a database:

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