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 bcnf boyce-codd normal form, BCNF Boyce-Codd Normal Form A rel...

BCNF Boyce-Codd Normal Form A relation schema R is in BCNF if it is in 3NF and accepts an additional constraint that for every FD X A, X has to be a candidate key. If a relati

Use the relational algebra to formulate query, Consider the following datab...

Consider the following database schema: STAFF(StaffNo, fName, lName, Position, sex, dob, branchNo) BRANCH(BranchNo, Street, City) Assume the following for the above database

Give concurrent sub states diagram for the classroom, Give Concurrent sub s...

Give Concurrent sub states diagram for the classroom and exam held. In Figure, simultaneous substrates have been taken. After passing Minor 1 test you could give Minor 2 test. T

Explain the disadvantages of creating a temporary table, Explain the disadv...

Explain the disadvantages of creating a temporary table? If you have already created a temporary table with a shown name and attempting to create a second one with that nam

In a relational model how relations are termed, In a relational model how r...

In a relational model how relations are termed? In a relational model, relations are termed as tables. (The term ‘relation’ is the technical name of the ‘table’ in RDBMS)

Write short notes on schema diagram, Write short notes on Schema diagram.  ...

Write short notes on Schema diagram.  A database schema along with primary key and foreign key dependencies can be depicted pictorially by schema  diagram. Every relation appea

Database Management System, Assume that you are responsible for selecting a...

Assume that you are responsible for selecting a new DBMS product for Sohar Hospital

Draw the dependency diagram for the relation, Consider the subsequent relat...

Consider the subsequent relation   Professor (Pfcode, dept, head, time)   It is assumed that      (i) A professor can work in much more than one

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