Alter table command, Database Management System

ALTER TABLE Command: This command is used for variation of existing structure of the table in the given situation:

  • When a new column is to be added to the table structure.
  • When the existing column definition has to be altered, i.e., changing the width of the data type or the data type itself.
  • When integrity constraints have to be dropped or included.
  • When a constraint has to be allowed or not allowed.

Syntax

ALTER TABLE

ADD ( ...); ALTER TABLE
MODIFY ( ...);

ALTER TABLE

ADD CONSTRAINT < constraint type>(field name);

ALTER TABLE

DROP;

ALTER TABLE

ENABLE/DISABLE ;

You require to put many constraints like that the database integrity is not compromised.

 

Posted Date: 3/11/2013 12:56:35 AM | Location : United States







Related Discussions:- Alter table command, Assignment Help, Ask Question on Alter table command, Get Answer, Expert's Help, Alter table command Discussions

Write discussion on Alter table command
Your posts are moderated
Related Questions
What is the use of a slotted-page structure and what is the information are there in the header? The slotted-page structure is used for organizing records within a one block.


What is 2NF? A relation schema R is in 2NF if it is in 1NF and every non-prime attribute A in R is fully functionally dependent on primary key.

Problem: A DBMS built for Online Transaction Processing (OLTP) is usually regarded as unsuitable for data warehousing. Each system is designed with a different set of requireme

Draw an entity relationship diagram (ERD) for the following situation: A company has a number of employees. Each employee is identified by an Employee_Id. The company wants to st

Question: This Question refers to the database schema given in the Appendix. (a) The integrity of a database is enforced by integrity rules. Discuss what should happen on a

What does Aggregation mean?

What is object containment? References among objects can be used to model dissimilar real-world concepts.

for the following business rules . Identify all entities, attributes, relationships, primary keys, cardinalities and constraints where appropriate 3. (9) An art museum owns a larg

Question: In relation to distributed database answer the following questions: (i) Give a brief definition of distributed database. Support your answer with an appropriate di