Top Posters
Since Sunday
27
26
25
22
21
21
21
20
20
20
19
19
New Topic  
wrote...
Posts: 125
2 weeks ago
Describe the reason why it is acceptable to have null foreign key, but it is unacceptable to have a null primary key. Use the concept of entity integrity rule and referential integrity rule in your answer.
Source  Download
Accounting Information Systems
Edition: 14th
Authors:
Read 7 times
1 Reply
Do What Makes You Come Alive
Replies
Answer verified by a subject expert
wrote...
Posts: 123
2 weeks ago
Sign in or Sign up in seconds to unlock everything.
A primary key cannot uniquely identify a row in a table if it is null (blank). A nonnull primary key ensures that every row in a table represents something and that it can be identified. This is referred to as the entity integrity rule. Foreign keys link rows in one table to rows in another table. This constraint, called the referential integrity rule, ensures database consistency. Foreign keys can contain null values.
1
Related Topics
New Topic      
Explore
Post your homework questions and get free online help from our incredible volunteers.
Learn More
Improve Grades
Help Others
Save Time
Accessible 24/7
  373 People Browsing
 132 Signed Up Today
Your Opinion
Which 'study break' activity do you find most distracting?
Votes: 153

Related Images
 1103
 6880
 365