Relation and relational schema, Database Management System

Assignment Help:

A relation has:

  • Relational Schema
  • Relation instance

Relational Schema:

A relational schema shows the relation's name, its attributes and the domain of every attribute. If R is the name of a relation and A1, A2...An is a list of attributes showing R then R (A1, A2...An) is known as a relational schema. Every attribute in this relational schema takes a value from some explicit domain called Domain (Ai).

For instance, the relational schema for relation PERSON as in Figure will be: PERSON (PERSON_ID:integer, NAME: string, AGE:integer, ADDRESS:string)

Total number of attributes in a relation indicates the degree of a relation. Hence the

PERSON relation includes four attributes, so this relation is of degree 4


Related Discussions:- Relation and relational schema

What subschema expresses, What subschema expresses ? A subschema expres...

What subschema expresses ? A subschema expresses the external view. (External schemas are called also called as subschemas)

What is the aim of logical schema, What is the aim of logical schema ? ...

What is the aim of logical schema ? The main motive of the logical schema is to ensure the portability of procedures and models on various physical schemas at runtime.

What is known as a search key, What is known as a search key? An attrib...

What is known as a search key? An attribute or set of attributes used to look up records in a file is known as a search key.

Query to list the employee name have 10000 salary, Consider employee table ...

Consider employee table of (i) and list names of department(s) for which average salary for department is more than 10,000. (SELECT d_name FROM dept WHERE d_code IN (SELECT d_c

What is the need for triggers, What is the need for triggers? Triggers ...

What is the need for triggers? Triggers are useful mechanisms for alerting humans or for starting particular tasks automatically when particular conditions are met.

Describe drop table command or cascade of sql, Describe DROP TABLE command ...

Describe DROP TABLE command of SQL along with both the options - CASCADE and RESTRICT. DROP TABLE command - This command drops the specified table. Dropping a table also dro

Keys, it can be possible to create any table without primary key

it can be possible to create any table without primary key

Creating database for library, i need help with creating database system fo...

i need help with creating database system for a library

What is odbc and what is its function, Question: (a) What is ODBC and w...

Question: (a) What is ODBC and what is its function? (b) What is Web application server, and how does it work from a database perspective? (c) What does e-commerce mean

What are the strategies of implementation of the statecharts, What are the ...

What are the different strategies of implementation of the Statecharts?  There are two strategies for implementation of state charts: i)   Basic Implementation Strategy

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd