Key constraint - relational constraints, Database Management System

Assignment Help:

This constraint shows that the key attribute value in each tuple must be unique, i.e., no two tuples have the similar value for the key attribute. This is because the value of the primary key is used to recognize the tuples in the relation.

 

Example: If A is the key attribute in the following relation R than A1, A2 and A3 must be unique.

 

A

 

B

 

A1

 

B1

 

A3

 

B2

 

A2

 

B2

 

Example: In relation PERSON, PERSON_ID is primary key so PERSON_ID cannot be given as the similar for two persons.

Integrity Constraint

There are two kinds of integrity constraints:

  • Entity Integrity Constraint
  • Referential Integrity Constraint

Related Discussions:- Key constraint - relational constraints

Create a table student with attributes student name, Question 1 Create a t...

Question 1 Create a table student with attributes student name, roll number, total marks and percentage. Do the following operations Insert details in to the table Update

Serialisable schedules, Serialisable Schedules: If the processes of two tra...

Serialisable Schedules: If the processes of two transactions conflict with each other, how to verify that no concurrency related problems have happened? For this, serialisability t

1) Information about a bank is about customer, 1) Information a...

1) Information about a bank is about customers and their account. Customer has a name, address which consists of house number, area and city, and one or more phone numbers. Ac

Accessing information permissions users, Accessing information about permis...

Accessing information about permissions to all users- Object level permissions: With the use of data dictionary you can see the permissions to user. Let us get the table name fro

#title using the invoice, using the invoice table shown below,write the rel...

using the invoice table shown below,write the relational schema,draw a dependencies,inclunding all partial and transitive dependencies.assume that the table does not contain repeat

Determine the two special events, What are two special events? The two ...

What are two special events? The two special events are as "entry" and "exit". Any action which is marked as linked to entry event is executed whenever given state is entered v

Explain the weak entity set, Explain the Weak Entity Set An Entity set...

Explain the Weak Entity Set An Entity set which does not have sufficient attribute to make a primay key is known as weak entity set. For instance, dependents of an employee in

Normalize table 3nf , Normalize the following tables upto and including the...

Normalize the following tables upto and including the 3NF. Submit a 1 page printout of only the final set of normalized tables in Data Architect. Just use Data Architect to do the

By the relations get details of employees working in sql, Consider the rela...

Consider the relations: PROJECT(proj#,proj_name,chief_architect) EMPLOYEE(emp#,emp_name) ASSIGNED(proj#,emp#) Use relational algebra to express the subsequent queries: (i) Get

Describe about use case and external case in dfd, Describe about Use Case a...

Describe about Use Case and external case in DFD The processes are transformed those into the Use Case and external case in DFD has same characteristics which of an actor in O

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