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 recovery management component? Ensuring durability is the responsibility of a software component of the base system known as the recovery management component.

Problem 1. Describe the following a) Advantages of Database Systems b) Functions of a DBMS Explanation of part (a) and (b) 2. Explain the following concepts w

What is System R? What are its two major subsystems? System R was intended and developed over a period of 1974-79 at IBM San Jose Research Center. It is a prototype and its pur

What is called a query evaluation plan? A sequence of primitive operations that can be used to assess a query is a query evaluation plan or a query implementation plan.

What is Oracle databse structure? Oracle database structure: The relational model has three main aspects: Structures: Structures are well-defined objects which store th

Describe the four main ways of optimising disk block access. Ans: a. Disk  b. Non-volatile writes buffers c. File organization (Clustering) d. Log-based file system

Wait-die" scheme : The idea is based on non-preventive method. It is based on a simple rule:                                 If Ti requests a database resource that is held by T

Define an abstraction by which relationships are treated as higher level entities Ans: Aggregation.  It is an abstraction by which relationships are treated as higher level

#question benefits and limitations of data models..

What is view in SQL? How is it defined? Any relation that is not part of the logical model, but is made visible to a user as a virtual relation is known as a view. We descri