Describe the Composite Key

Composite Key: Sometimes one key is not enough to uniquely recognize a row. E.g. in a single class Roll is enough to search a student, but in the whole school, merely searching by the Roll is not enough, because there could be 10 classes in the school and every one of them may have a certain roll no 5. To uniquely recognize the student we have to say something like "class VII, roll no 5". So, a combination of two or more attributes is combined to make a unique combination of values, such as Class + Roll.

 

Posted Date: 7/26/2013 6:12:39 AM | Location : United States

Ask an Expert

Related Discussions:- Describe the composite key, Assignment Help, Ask Question on Describe the composite key, Get Answer, Expert's Help, Describe the composite key Discussions

Write discussion on Describe the composite key
Your posts are moderated

Write your message here..

Related Questions

Describe analysis of access paths, Describe analysis of access paths To... Describe analysis of access paths To describe analysis of access paths, consider an example of the design of a company's employee skills database. A part of the object model fr

Er diagram, a publishing company produce scientific books on various subjec... a publishing company produce scientific books on various subjects. the books are written by authors who specialize in one particular subject. the company employs editors who, not n

What is d command work in the respect of qbe, What is D command work in the... What is D command work in the respect of QBE? D: It is the command inside QBE to delete tuple(s) from the relation.

ER Diagram, Hi I have got an assignment for making an er diagram for market... Hi I have got an assignment for making an er diagram for market management software can any budy help me?

Horizontal Fragmentation, I want to fragment existing table using java code... I want to fragment existing table using java code... help me..!!

Inheritance, what is relationship inheritance and attribute inheritance what is relationship inheritance and attribute inheritance

Database, A database has been designed for this beauty parlour in order for... A database has been designed for this beauty parlour in order for the staff to manage specific things such as bookings made by clients, payments, staff availability, level of exper

What is the meaning of recovery, What is the meaning of Recovery? In d... What is the meaning of Recovery? In deferred update methods, if a transaction fails before arriving its commit point, it will not have altered the database in any way, so UNDO

Explain about primary key, Explain about primary key Primary Key: It ... Explain about primary key Primary Key: It is one of the candidate keys that are taken to be the recognizing key for the entire table. E.g. although there are two candidate ke

What is a name, What is a Name? A user-supplied name is used for identi... What is a Name? A user-supplied name is used for identity. This form of identity is used for files in file systems. The user gives every file a name that uniquely identifies it