What is the difference between primary key and a unique key, Database Management System

Assignment Help:

What's the difference between a primary key and a unique key?

Both primary key and unique key enforces uniqueness of the column on which they are explained. But by default primary key creates a clustered index on the column, where are unique makes a no clustered index by default. Another main difference is that, primary key doesn't permit NULLs, but unique key permits one NULL only.

 


Related Discussions:- What is the difference between primary key and a unique key

Explain trivial dependency, Explain trivial dependency? Functional depe...

Explain trivial dependency? Functional dependency of the form α ->β. is trivial if α C β. Trivial functional dependencies are satisfied by all the relations.

Decomposition properteis, what is lossless & dependency preserving decompo...

what is lossless & dependency preserving decomposition ?

Process-oriented decompositions, Process-oriented decompositions Pr...

Process-oriented decompositions Process-oriented decompositions divide complex process, task or function into simpler sub processes until they get simple enough to be deal

Basic set operation, These are the binary operations; i.e., each is applied...

These are the binary operations; i.e., each is applied to two relations or sets. These two relations can be union compatible excluding in case of Cartesian product. Two relations R

What is specialization, What is Specialization? Specialization: Special...

What is Specialization? Specialization: Specialization permits you to describe new types of information (new structural types or latest domains of information), although reusin

Er diatgrams, Ask q“A database will be made to store information about pati...

Ask q“A database will be made to store information about patients in a hospital. On arrival, each patient’s personal details (name, address, and telephone number) are recorded wher

What is database files , The database files accept the actual data and ...

The database files accept the actual data and are typically the biggest in size. Depending on their shape, the tables for all the user operation can go in one database file-but

Datawarehouse Case studies, I have been given 8 differebt data warehouseing...

I have been given 8 differebt data warehouseing failure case studies. I need to question 4 questions for each

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

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