Referential integrity, Database Management System

Assignment Help:

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.


Related Discussions:- Referential integrity

Create a view that finds the student name, Section A:  Use the following ta...

Section A:  Use the following tables to create a database called College.  Use SQL commands. Student stuid(primary) lastName firstName

What are the uses of functional dependencies, What are the uses of function...

What are the uses of functional dependencies? To test relations to see whether they are legal under a given set of functional dependencies. To state constraints on the set

What is the object-oriented decompositions, Object-oriented decompositions ...

Object-oriented decompositions Object-oriented decompositions of systems better are able to cope with change. Each subsystem has a well-defined interface which communicates with

What way a particular application views data from database, What is the way...

What is the way a particular application views the data from the database that the application uses? Sub schema is the way a particular application views the data from the data

What are segments in oracle, What are segments in oracle? Segments - Ea...

What are segments in oracle? Segments - Each table has single field of disk space, known as segment, set aside for it in the tablespace. Segments consist of contiguous sections

Create a e-r diagram or uml class diagram, We require an advanced system fo...

We require an advanced system for a Sports Centre, you are concerned only with representing the data discussed below about bookings and members. (The complete system may contain ot

What is vertical fragmentation, What is vertical fragmentation? Vertica...

What is vertical fragmentation? Vertical fragmentation divides the relation by decomposing the scheme R of relation r.

Conflicting operations in schedule, Conflicting Operations in Schedule: ...

Conflicting Operations in Schedule: The three simple ways of interleaved instruction implement of transactions T1 and T2. Please note that in the following tables the first col

Construct a generalization-specialization hierarchy, Construct a generaliza...

Construct a generalization-specialization hierarchy for a motor-vehicle sales company. The company sells motorcycles that comprise an engine number and cost; cars that have a chass

Create role named roletable to allows a user to create table, Create role n...

Create role named role_table that allows a user to create tables. Using role_table allow users kripa and reena to create tables. CREATE ROLE role_table; GRANT CREATE ANY TABLE

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