Explain cascade and restrict clauses of drop schema command, Database Management System

Assignment Help:

Explain several types of constraints that can be specified using CREATE TABLE command. Explain CASCADE and RESTRICT clauses of DROP SCHEMA command?

Constraint Description
PRIMARY KEY Determines that column(s) uniquely identifies each record. The primary key cannot be NULL, and the data value(s) must be unique.

FOREIGN KEY In a one-to-many relationship, the constraint is added to the "many" table. The constraint ensures which if a value is entered into a specified column, it must already exist in the "one" table, or the record is not added.

UNIQUE Ensures that all data values stored in a specified column are unique.
The UNIQUE constraint differs from the PRIMARY KEY constraint in which it permits NULL values.
CHECK Ensures in which a specified condition is true before the data value is added to a table. For example, an order's ship date cannot be previous than its order date.

NOT NULL Ensures in which a specified column cannon contain a NULL value. The NOT NULL constraint can just be created along with the column-level approach to table creation.

Prevents the DROP from taking place if any dependent objects exists (RESTRICT) or causes all dependent objects do also be dropped (CASCADE).


Related Discussions:- Explain cascade and restrict clauses of drop schema command

How can you start mysql server, How can you Start MySQL Server? To star...

How can you Start MySQL Server? To start the mysql program type it is name in the command- line prompt. After starting mysql program just display A welcome letter using the

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.

Which model is record based logical model, Which model is record based logi...

Which model is record based logical model? Network Modelis basically known as record based logical model.

#title using the invoice, using the invoice table shown below,write the rel...

using the invoice table shown below,write the relational schema,draw a dependencies,inclunding all partial and transitive dependencies.assume that the table does not contain repeat

relationship with the owner entity, A database for the Service and Mainten...

A database for the Service and Maintenance (SM) section of a Computer sales and service Company has to be developed. SM gives after sales service to customers. SM branch has a numb

Research in Concurency Control Protocols, Performance of Various Concurrenc...

Performance of Various Concurrency Control Mechanisms

Design of a database, Ask questioYou are the database administrator in a un...

Ask questioYou are the database administrator in a university. You have been tasked to come up with a new database for the University. Using the stages in Database Life Cycle come

Explain the rules for creating a labelled precedence graph, Explain the rul...

Explain the rules for creating a labelled precedence graph for testing view serializability.            Ans: A schedule S is view serializable if it is view equivalent to a ser

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