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

What are the dbms languages, What are the DBMS languages? Explain.  Ans...

What are the DBMS languages? Explain.  Ans: a) Data Definition Languages (DDL): It is employed to specify database schema for example CREATE DROP statements etc.     b)  Dat

Create a view that finds the student name, Section A:  Use the following ta...

Section A:  Use the following tables to create a database called College.  Use SQL commands. Student stuid(primary) lastName firstName

Explain candidate key, Explain Candidate key? Candidate Key - A candi...

Explain Candidate key? Candidate Key - A candidate key is a minimal superkey, that can be used to uniquely identify a tuple in the relation.

Schema, difference between internal schema and external schema in DBMS

difference between internal schema and external schema in DBMS

Er schema can be represented by relation schemas , Q. Describe how an ER sc...

Q. Describe how an ER schema can be represented by relation schemas and constraints arising from ER design can be mapped to constraints on a relation schema.     The entity rela

Why object-oriented system use the relational dbms, Why, generally does an ...

Why, generally does an object-oriented system use the relational DBMS? The reasons for using relational DBMS for OO systems could be any combination of following: a. Many or

Client server databases, Client Server Databases- The concept behind the C...

Client Server Databases- The concept behind the Client/Server systems is simultaneous, cooperative processing. It is an approach that presents a one systems view from a user's vie

Explain clustering file organization, Explain Clustering file organization ...

Explain Clustering file organization (i) Determine if a record of file is physically ordered on a nonkey field - that does not comprise a different value for each record - that

Database administrator, Database Administrator One of the main perpos...

Database Administrator One of the main perpose for having the database management system is to have control of both data or programs accessing that data. The person having li

Union - basic set operation, UNION If R1 and R2 are two union compatibl...

UNION If R1 and R2 are two union compatible relations then R3 = R1 ∪ R2 is the relation having tuples that are either in R1 or in R2 or in both. In case, R3 will have tuples

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