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

Physical model of traffic data management, After the completion of the logi...

After the completion of the logical model the physical model is to be made. The oracle 10 G will be used as a database server and all the tables with their column are created and i

Determine the operation that do not participate to be union, 1. Which relat...

1. Which relational algebra operations do not need the participating tables to be union-compatible? Ans: Join is the relational algebra operations that do not need the particip

Explain sorted file with advantages, Explain sorted File with advantages? ...

Explain sorted File with advantages?  Sorted file The sort utility shall perform one of the subsequent functions: 1.Sort lines of all the named files together and write the

DISTIBUTED DATABASE, Define physical image of a global relation at a site

Define physical image of a global relation at a site

Statistical analysis of data, An important first step to the statistical an...

An important first step to the statistical analysis of data is to "get to know your data".  The following tasks should contribute to this. (a)   To the right of the dataset cons

Increased overheads on update-data replication, Increased overheads on upda...

Increased overheads on update : On the drawbacks side, it will need the system to ensure that all replicas of a relation are consistent. This shows that all the replicas of the rel

Describe logical data independence, Describe logical data independence ? ...

Describe logical data independence ? Logical Data Independence - It is the capacity to modify the conceptual schema without having to change external schemas or application p

Implementing a data warehouse, (a) Data warehouse can be defined as "a sub...

(a) Data warehouse can be defined as "a subject-oriented, integrated, time-variant, non-volatile collection of data" in support of management's decision making process. Explain ea

Log, what is the need of a log in dbms

what is the need of a log in dbms

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