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

What are the issues are formed while selecting a database, What are the Iss...

What are the Issues when Selecting a Database Issues when Selecting a Database Storage space requirement: A database requires about triple storage space of the actua

Discuss difference between drop table r and delete from r, Discuss The diff...

Discuss The difference between drop table R and delete from R.  DROP TABLE command deletes all the records with the table definition. This command will automatically committed

Define the five basic operators of relational algebra, Define the five basi...

Define the five basic operators of relational algebra? Five basic operators of relational algebra are: 1. Union (∪∪∪∪) - Selects tuples which are in either P or Q or in both

Compare the efficiency of the two mining processes, Consider the following ...

Consider the following database containing five transactions. Let min_sup = 60%. Mine all frequent itemsets using Apriori and FP-growth algorithm. Compare the efficiency of the t

What is the full form of odbc, What is the full form of ODBC ? ODBC stand...

What is the full form of ODBC ? ODBC stands for Open Database Connectivity.

Data fragmentation in distributed database system, brief history,definition...

brief history,definition,current trends and future trends if any of data fragmentation

What are the advantages of object oriented databases, What are the advantag...

What are the advantages of object oriented databases in comparison with others? Why it is still not widely used? Object oriented designs are coherent, efficient and less prone

Create a view containing name and number of department, Create a view emp_d...

Create a view emp_dep containing e_name and number of dependents from the tables employee and dependent of (i) CREATE VIEW emp_dept AS SELECT ename, COUNT(*) FROM employee, dep

Explain the operation of the data warehouse, Using a labelled diagram expla...

Using a labelled diagram explain the operation of the Data Warehouse, define the basic architectural components and outline the main functionalities. Briefly explain the role an op

Special workarea for interface, While using extract datasets it is required...

While using extract datasets it is required to have a special workarea for interface False.  It is not required to have a special workarea for interface

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