Entity integrity constraint - relational constraints, Database Management System

Assignment Help:

It defines that no primary key value can be null. This is as the primary key is used to recognize individual tuple in the relation. So we will not be able to recognize the records uniquely containing null values for the primary key attributes. This constraint is specified on single individual relation.

 Example: Let R be the Table

A#

B

C

Null

B1

C1

A2

B2

C2

Null

B3

C3

A4

B4

C3

A5

B1

C5

Note:

1) '#' shows the Primary key of a relation.

In the relation R above, the primary key has null values in the tuples t1 & t3. NULL value in primary key is not allowed, therefore, relation instance is an invalid instance.


Related Discussions:- Entity integrity constraint - relational constraints

Define 2nf normal form, 2NF Normal Form : A relation schema process R i...

2NF Normal Form : A relation schema process R is in 2NF if it is in 1NF and each non-prime attribute A in R is fully functionally related on primary key. Second normal form (2N

How relational calculus is different from relational algebra, How Relationa...

How Relational Calculus is different from Relational Algebra? What do understand by TRC queries and DRC queries?  Ans: Relational calculus contain two calculi, the tuple relati

Explain the function of input controls, Explain the function of input contr...

Explain the function of input controls. Identify four types of input control and explain the function of each. Provide an example of a data integrity error that could occur i

What are the disadvantages of relational data, What are the disadvantages o...

What are the disadvantages of relational data ? Disadvantages • Performance - If the number of tables among that relationships to be established are large and the tables t

Data models, why older data models are being replaced by new data models....

why older data models are being replaced by new data models.

What type of view of total database content, What type of view of total dat...

What type of view of total database content? Data base content Conceptual view of total database contain.

What is the meaning of redundant associations, Adding Redundant Association...

Adding Redundant Associations for Efficient Access The expression redundant association means using "duplicate association for proficient access". While analysis, it is not a

Relational algebraic operators, Problem Explain at least five relationa...

Problem Explain at least five relational algebraic operators with a suitable example. Note: All the above descriptions should be done by taking at least two examples from ou

Method of analyzing association traversal, Analyzing Association Traversal ...

Analyzing Association Traversal Till now, we have supposed that associations are bi-directional. But in the case of traversal, it is in only one direction in any application,

Define shadow paging, Define shadow paging. An alternative to log-based...

Define shadow paging. An alternative to log-based crash recovery method is shadow paging. This technique requires fewer disk accesses than do the log-based methods.

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