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

Determine the term- active values, Determine the term- Active values An...

Determine the term- Active values An active value is that has dependent values. Every dependent value registers itself with active value that contains a set of dependent values

Unix System Administration, What Command You Use What Day of the week were ...

What Command You Use What Day of the week were you born

Explain the lock based protocol, Lock Based Protocol A lock is nothing ...

Lock Based Protocol A lock is nothing but a mechanism that tells the DBMS whether a particular data item is being used by any transaction for read/write purpose. As there are t

Dbms, Retrieve the S&S In-Chapter Database (in Microsoft Access format) fro...

Retrieve the S&S In-Chapter Database (in Microsoft Access format) from the text's Web site (or create the tables in Table 4-5 in a relational DBMS product). Write queries to answer

What is candidate key, What is candidate key? Candidate Key - A candi...

What is candidate key? Candidate Key - A candidate key of an entity set is a minimal superkey, which uniquely identifies each row in the relation.

Er digrams, what is er digram given that example of hospital,bank and libra...

what is er digram given that example of hospital,bank and library er digram.

Create a table for database transformation , Step 1 . Using Oracle, create ...

Step 1 . Using Oracle, create the tables identified in the preferred solution for Assignment 2. Technicians (ZipCode, TechnicianID, FirstName, LastName, Street, City, State, Home

Student database, tell me the functionality,advantages and disadvantages of...

tell me the functionality,advantages and disadvantages of student database

Explain the concept of deadlock, Explain the concept of deadlock Yes. I...

Explain the concept of deadlock Yes. It can direct to deadlock. Suppose that a batch of frames arrived correctly and were accepted. Then receiver will advance its window. Now s

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