Explain the integrity constraints, Database Management System

Assignment Help:

Explain the integrity constraints: Not Null,  Unique, Primary Key with an example each. Is the combination 'Not Null, Primary Key' a valid combination. Justify.

Not Null - Should hold valid values and cannot be NULL.

Unique - An attribute or a combination of two or more attributes must have a unique value in each row. The unique key can have NULL values.

Primary Key - It is similar as unique key but cannot have NULL values. A table can have at most one primary key in it.

For example:

STUDENT

Roll No

Name

City

Mobile

 

17

Ankit Vats

Delhi

9891663808

16

Vivek rajput

Meerut

9891468487

6

Vanita

Punjab

NULL

75

Bhavya

delhi

9810618396

Roll No is a primary key.

Name is defined with NOT NULL, means each student must have a name.

'Not Null, Primary Key' is a valid combination. Primary key constraint already includes

'Not Null' constraint in it but we can also add 'Not Null' constraint with it. The use of

'Not Null' with 'Primary Key' will not have any effect. It is same as if we are using just 'Primary Key'.


Related Discussions:- Explain the integrity constraints

Express types of information available in mysql, Express types of informati...

Express types of information available in MySQL? Information as regards the result of queries:  This includes number of records affected by any SELECT or UPDATE or DELETE st

Homework, can you resolve this for me please? Database Management Systems ...

can you resolve this for me please? Database Management Systems Homework 1 The following relations are given (primary keys are underlined): PLAY-ACTOR(AId, Name, Nationality, Birt

What is difference between primary index and secondary index, What is diffe...

What is difference between primary index and secondary index? Primary Index a) It is an ordered file whose records are of fixed length along with two fields. b) Only base

Which steps must designer take to adjust inheritance, In object oriented de...

In object oriented design, which steps must designer take to adjust inheritance? To readjust inheritance following steps should be taken: i)  Rearrange and adjust the classe

What is recursive closure and operation relational algebra, What is recursi...

What is recursive closure? Why is it not possible to describe this operation in relational algebra? Recursive closure is applied to recursive relationship. An instance of rec

Illustrate the term- abstracting out common behaviour, Illustrate the term-...

Illustrate the term- Abstracting Out Common Behaviour Inheritance is not every time recognised during analysis phase of development, thus it is necessary to re-evaluate object

Explain different types of keys and relational model., Relational Model: T...

Relational Model: The relational model uses a collection of tables to represent both data and the relationships among those data. Each table has multiple columns and each column h

Design an entity relation model, Funky Festivals Specification Funky Fe...

Funky Festivals Specification Funky Festivals organise music festivals which take place at various venues throughout the UK.  A venue needs to be booked before a Festival can t

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