Key constraint - relational constraints, Database Management System

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.


















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
Posted Date: 3/6/2013 5:30:34 AM | Location : United States

Related Discussions:- Key constraint - relational constraints, Assignment Help, Ask Question on Key constraint - relational constraints, Get Answer, Expert's Help, Key constraint - relational constraints Discussions

Write discussion on Key constraint - relational constraints
Your posts are moderated
Related Questions
Develop Database academic assignment Project Description: For a provided set of instructions in a case study design Entity Relationship Diagram. - Entity Relationship Diag

i am required to come up with entities relationships, optionality and cardinality from a scenario. there is a night club and bookings for a musician band

Why a report generator is used ? Report generator is used for print files on paper.

Can we delete data element, which is being used by table fields. No we cant delete data element.

Describe disk manager and their work? Disk Manager: Responsible for fetching data regulated through file Manager from disk storage within Main memory and deciding what data to

Define Hash files organization a. Hashing includes computing the address of a data item by calculating a function on the search key value.   b. A hash function h is a functi

what do you understand by enhanced entity-relationship

What is indexed sequential file organization? What are the applications of this organization?  Ans: An index file can be employed to effectively overcome the problem of storing

find a name whose address is erode from student table

What are the key features of Oracle? Key features of Oracle are as follows: • Read Consistency • Concurrency • Locking Mechanisms • Quiesce Database • RAC • Portability