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

Logical design part 1, create an e-r diagram usuing graphical dipicted soft...

create an e-r diagram usuing graphical dipicted software that could theoritically be used in resturant application

desirable properties of decomposition, Desirable Properties Of Decompositi...

Desirable Properties Of Decomposition Decomposition is a process of dividing a relation into its projections that will not be disjoint. Please remind the Relational projection

How to rearrange the execution order for efficiency, Rearrange the Executio...

Rearrange the Execution Order for Efficiency  Rearranging execution order for efficiency means executing such job that requires less execution time. By rearranging the object

What is meant by physical blocks, What is meant by Physical blocks? The...

What is meant by Physical blocks? The input and output operations are completed in block units. The blocks residing on the disk are referred to as physical blocks.

Define cardinality and participation constraints, Define cardinality and pa...

Define cardinality and participation constraints on a relationship type, completeness constraint on generalization.        Ans: Cardinality defines the number of entities to wh

Fragmentation-design of distributed databases, Fragmentation: It is defini...

Fragmentation: It is definite as partitioning of a relation into various fragments.Every fragment can be stored at a dissimilar site.

Describe specialsation and generalization, Describe Specialsation and gener...

Describe Specialsation and generalization? Specialisation /generalization: This is a top down and bottom up approach to the design of database. It displays the IS_A relation

Relationship cardinality, Cardinality shows the number of instances of an e...

Cardinality shows the number of instances of an entity associated with another entity participating in a relationship. Depend on the cardinality binary relationship can be further

What is asterisk in sql, What is Asterisk in SQL? Asterisk (*): In SQL,...

What is Asterisk in SQL? Asterisk (*): In SQL, the columns for all the tables and views in the FROM clause will be displayed.

Describe sequential file organization, Describe sequential file organizatio...

Describe sequential file organization.  Explain the rules for (i)  Inserting a new record. (ii)  Deleting an existing record.          Ans:A sequential f

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