Column constraints, Database Management System

Assignment Help:

Column Constraints: NOT NULL, UNIQUE, CHECK, PRIMARY KEY, DEFAULT, REFERENCES,

On  delete  Cascade:  Using  this  key  whenever  a  parent  row  is  removed  in  a referenced table then all the corresponding child rows are removed from the referencing table. This constraint is a form of referential integrity constraint.

Example 1:

CREATE TABLE product

(

pno number (4) PRIMARY KEY, pname char (20) NOT NULL,

qoh number (5) DEFAULT (100),

 class char (1) NOT NULL,

rate number (8,2) NOT NULL,

CHECK ((class='A' AND rate<1000) OR (class='B' AND rate>1000 AND rate<4500) OR (class='C' AND rate>4500))

);

The command above makes a table. Primary key constraint makes sure that product number (pno) is not null and unique (both are the properties of primary key). Please note down the use of data type char (20). In many executions of SQL on commercial DBMS such as Oracle and SQL server, a data type known as varchar and varchar2 is used respectively. Varchar mainly is variable length character type subject to a maximum specified in the declarations. We will use them at most of the places soon.

Please note the use of check constraints in the table formed above. It correlates two dissimilar attribute values.


Related Discussions:- Column constraints

horizontal fragmentation, Horizontal Fragmentation- Horizontal fragmentati...

Horizontal Fragmentation- Horizontal fragmentation groups together the tuples in a relation that are collectively used by the main transactions. A horizontal fragment is produced b

When it is better to use files than a dbms, When It is better to use files ...

When It is better to use files than a DBMS? It is better to use files than a DBMS when Multiple users wish to access the data.

Define transitive dependencies, What do you understand by transitive depend...

What do you understand by transitive dependencies? Define with an example any two problems that can take place in the database if transitive dependencies are available in the datab

Why like predicate used for, Why Like predicate used for? LIKE predicat...

Why Like predicate used for? LIKE predicate: The LIKE predicate searches for strings in which have a certain pattern.

Create a customer database and apply queries, For the question given below,...

For the question given below, you are required to submit design and implementation documentation as described over the page. Design, implement (in Java), test and document a set of

File handling and classes, Write the C++ program having class name studenti...

Write the C++ program having class name studentinfo, that is used to store the VU student information: This class should store your VUID, campus id, name and father name in the fol

What is oracle process explain for processes of oracle, What is Oracle Proc...

What is Oracle Process? Explain any four processes started by Oracle. Oracle Process is as follows: SMON: The System Monitor carries out a crash recovery while a crashed in

Database Normalization, I have a homework assignment due today by midnight....

I have a homework assignment due today by midnight. I need help understanding databasse normalization and determining the type of form violation & how to fix the violation.

What is a view, What is a view? A view is a logical view on one or more...

What is a view? A view is a logical view on one or more tables.  A view on one or more tables i.e., the data from a view is not actually physically kept instead being derived 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