IT_163_Midterm Project_Unit 5

IT_163_Midterm Project_Unit 5 - Midterm Project Question 1:...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Midterm Project Question 1: Define Referential Integrity- Referential Integrity means that the foreign key must match the primary key of a referenced table or be null. It is impossible to delete a row whose primary key has a matching foreign key in another table. Remember that through referential integrity, it is possible for a customer not to have a sales rep number, but it is not possible for a customer to have an INVALID sales rep number. What does that mean? It is possible for a customer not to have a sales rep number, but it is not possible for a customer to have invalid sales rep. number means that if the customer has a number, that number must be associated coherently with the rest of the database, but they can still not have a number. Example: Kathie has an id because she has made a purchase. Another table associates that id with his list of purchases. John does not have an id, because he has not made a purchase. There are no people in the database with an invalid id. If Jane had an id, but no list of purchases, that would violate referential integrity.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 09/25/2010 for the course IT IT163 taught by Professor Baylor during the Spring '10 term at Kaplan University.

Page1 / 2

IT_163_Midterm Project_Unit 5 - Midterm Project Question 1:...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online