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

Develop database academic assignment, Develop Database academic assignment ...

Develop Database academic assignment Project Description: For a provided set of instructions in a case study design Entity Relationship Diagram. - Entity Relationship Diag

Explain interfaces for parametric users, Explain Interfaces for parametric ...

Explain Interfaces for parametric Users? Interfaces for Parametric Users - Parametric users, such as bank tellers, frequent have a little set of operations in which they must p

Explain normalization, What is Normalization? Database normalization is...

What is Normalization? Database normalization is a data design and organization method applied to data structures based on rules that help building relational databases. In rel

Need for client server computing, Need for Client Server Computing- Client/...

Need for Client Server Computing- Client/Server (C/S) architecture includes running the application on multiple machines in which every machine with its component software tackles

Hello, Java program for horrizontal fragmentation in distributed database

Java program for horrizontal fragmentation in distributed database

What are the objectives of advance object design, What are the Objectives o...

What are the Objectives of Advance object design After this unit, you shall be able to: combine three OOAD models to obtain operations on the classes; develop algo

Represent the form as a relational schema, Question: This form represen...

Question: This form represents one of a number used for each sailing of a range of boats. A passenger may go on many sailings and will have the same passenger number for each.

Explain what is ddl, Explain what is DDL? DDL - Data Definition Languag...

Explain what is DDL? DDL - Data Definition Language: statements used to define the database structure or schema. Some examples: CREATE - to create objects in the database ALT

Search the name department number and salary of employees , Example : Searc...

Example : Search the name, department number and salary of employees drawing minimum salary in that department. SELECT ENAME, SAL, DEPTNO  FROM EMP WHERE SAL IN (SELECT MI

Write a query that uses the union operator, Write a Query that uses the UNI...

Write a Query that uses the UNION Operator 1. Use the Software Experts database to:   a. Display the first and the last name of all consultants who worked on any projects 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