Alter table command, Database Management System

Assignment Help:

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.

 


Related Discussions:- Alter table command

Draw entity relationship diagram, Draw entity relationship diagram for the ...

Draw entity relationship diagram for the following scenario. A university has many departments whereas each department belongs to that particular uni. That uni has also many bui

File Management Principles, What are the requirements to ensure the objecti...

What are the requirements to ensure the objectives of file management principle is realized?

What are the properties of transaction, What are the properties of transact...

What are the properties of transaction? There are three properties of transactions :- A)     Atomicity B)      Consistency C)       Isolation

What is meant by heuristic optimisation, What is meant by heuristic optimis...

What is meant by heuristic optimisation?  Discuss the main heuristics that are applied during query optimisation.  Ans:  In heuristic optimization, heuristics are employed to r

What is normalization, What is normalization? It is a method of analysi...

What is normalization? It is a method of analysing the given relation schemas based on their Functional Dependencies (FDs) and primary key to attain the properties (1).Minim

RAID technology, what characterizes the levels in RAID technology

what characterizes the levels in RAID technology

Convert the erd into its relevant relational schema, Question: Describe...

Question: Describe briefly the three parts of the Relational Model. (a) The term integrity refers to the accuracy or correctness of the data in the database. Define the fol

Support by adding indexes, Support by Adding Indexes Multiple indexes c...

Support by Adding Indexes Multiple indexes can be used to access a data file by multiple access paths. In such a scheme only single copy of the data is consider, only the numbe

3NF, Winfield is a small city with a population of 22,000 with buses serves...

Winfield is a small city with a population of 22,000 with buses serves three routes in Winfield and neighboring areas. As the city’s IT director, you have been asked to set up an i

Define partial, Partial Key : It is a group of attributes that can uniquel...

Partial Key : It is a group of attributes that can uniquely identify small entities and that are related to same base entity. It is sometime named as Discriminator.  Altern

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