What is a foreign key, Database Management System

Assignment Help:

What is a foreign key, and what is it used for?

A foreign key is used to establish relationships between relations in the relational model. Technically, a foreign key is a column (or columns) appearing in one relation that is (are) the primary key of another table. Although there might be exceptions, the values in the foreign key columns usually must correspond to values existing in the set of primary key values. This correspondence necessity is created in a database using a referential integrity constraint on the foreign key.

 

 


Related Discussions:- What is a foreign key

What is a recursive relationship, Question: (a) Can a set of data requi...

Question: (a) Can a set of data requirements be correctly modelled by two or more different ER diagrams? Explain your answer. You may use a small example, if you think it will

What is object oriented model, What is Object Oriented model? This mod...

What is Object Oriented model? This model is based on collection of objects. An object has values stored in instance variables with in the object. An object also having bodies

Derived horizontal fragmentation, atient(PNumber, Name, NHS_no, Amount_due,...

atient(PNumber, Name, NHS_no, Amount_due, DNO, Doctor, Medical_Treatment), relation of schema Staff(StaffNum, Name, DNO, Task) and relation of schema Dept(DNO, Name, Location, Dire

How do you find the final model after iterative analysis, How do you find t...

How do you find the final model after iterative analysis? Why is iterative analysis of any of the problem needed? The final model serves as the base for system architectur

Critically evaluate the bulleted list of information, Critically evaluate t...

Critically evaluate the bulleted list of information-related items in this case study. How are each contradictory to the notion of being an information-literate knowledge worker?

Create a e-r diagram, Information about films holds information about movie...

Information about films holds information about movies, stars and studios. Movies have a title, year of production, length and the film type. Stars have a name and address. Studi

Abap/4 program, It is not possible to make an ABAP/4 program, which having ...

It is not possible to make an ABAP/4 program, which having only Subroutines. False. We can make ABAP/4 program, which having only Subroutines.

Data modelling, Law Associates is a large legal practice based in Sydney.  ...

Law Associates is a large legal practice based in Sydney.  You have been asked to design a data model for the practice based upon the following specification: The practice emplo

What is the main advantage of the object model, What is the main advantage ...

What is the main advantage of the object model? What are its different components? The object model focuses on the logical data structures. Each object model comprises of many

Create table, What are the advantages of creating a table from existing tab...

What are the advantages of creating a table from existing 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