Referential integrity, Database Management System

It can be easily defined as:

The database must not have any unmatched foreign key values.

The term "unmatched foreign key value" means a foreign key value for which there does not exist a matching value of the relevant candidate key in the relevant target (referenced) relation. For instance, any value existing in the EMPID attribute in ASSIGNMENT relation must be in the EMPLOYEE relation. That is, the only EMPIDs that can be in the EMPLOYEE relation are 101, 102 and 103 for the instance / present state of the database given in Figure. If we want to insert a tuple with EMPID value 104 in the ASSIGNMENT relation, it will cause violation of referential integrity constraint. Logically it is very obvious after all the employee 104 does not be, so how can s/he be assigned any work.

Posted Date: 3/6/2013 6:37:38 AM | Location : United States







Related Discussions:- Referential integrity, Assignment Help, Ask Question on Referential integrity, Get Answer, Expert's Help, Referential integrity Discussions

Write discussion on Referential integrity
Your posts are moderated
Related Questions
PART MARKING:  We will only mark TWO of the four questions below but you must submit answers to all four. We will choose the questions we mark randomly and we will supply you with

external and internal mapping with examples

Single Valued Normalisation  Codd in the year 1972 formed three normal forms (1NF, 2NF, and 3NF). These were based on functional dependencies between the attributes of a relati

create an e-r diagram usuing graphical dipicted software that could theoritically be used in resturant application

Differentiate strict two phase locking protocol and rigorous two phase locking protocol. In strict two phase locking protocol all exclusive mode locks taken by a transaction is

Designing the fields in the data base The following are the considerations one has to remain in mind while designing the fields in the data base. Coding, compression, en

Why are cursors necessary in embedded SQL? A cursor is an object used to store the output of a query for row-by-row processing through the application programs. SQL statements

Data Replication "If a relation R has its copies kept at two or more sites, then it is considered replicated". But why do we replicate a relation? There are several advan

Determine the Strong and Weak Entity Based on the method of foreign key, there might be arise a situation when we have to relate an entity having a primary key of its own and a

A relation has: Relational Schema Relation instance Relational Schema: A relational schema shows the relation's name, its attributes and the domain of every a