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

What features relational dbms contribute level of integrity, A well-maintai...

A well-maintained relational DBMS has a high level of data integrity. What features of a relational DBMS contribute towards this level of integrity? Relational DBMS gives high

Difference among a database schema and a database state, What is the differ...

What is the difference among a database schema and a database state? The collection of information stored in database at particular moment in time is known as database state a

What are the features of embedded sql explain, What are the features of emb...

What are the features of embedded SQL? Explain. Embedded SQL - SQL could be implemented within two ways. It can be used interactively or embedded in a host language or throu

View of data, how to submit answers softcopy

how to submit answers softcopy

Aims of the design project, The aims of the project are: 1. To enable th...

The aims of the project are: 1. To enable the students to undertake the detailed design of a specific plant or process 2. The design projects includes: process selection; und

Statistical analysis of data, An important first step to the statistical an...

An important first step to the statistical analysis of data is to "get to know your data".  The following tasks should contribute to this. (a)   To the right of the dataset cons

Define the concept of design documentation, Design Documentation  The ...

Design Documentation  The Design Document shall be an extension of Requirements Analysis Design. "The Design Document will comprise a revised and much more detailed descrip

Explain strict two-phase locking, Explain Strict Two-Phase locking A tr...

Explain Strict Two-Phase locking A transaction T does not release any type of its exclusive (X) locks until that transaction commits or aborts. In this method no other transact

Describe the composite key, Describe the Composite Key Composite Key: ...

Describe the Composite Key Composite Key: Sometimes one key is not enough to uniquely recognize a row. E.g. in a single class Roll is enough to search a student, but in the w

What is database trigger, What is database Trigger? A database trigger ...

What is database Trigger? A database trigger is a PL/SQL block that can explained to automatically execute for insert, update, and delete statements against a table. The trigge

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