Showing posts with label Database. Show all posts
Showing posts with label Database. Show all posts
Sunday, 1 June 2014
Wednesday, 21 May 2014
Difference Between Database and Data Warehouse
Tuesday, 20 May 2014
Difference Between Data Mining and Machine Learning
Wednesday, 8 May 2013
Database Management System (DBMS) Interfaces
DBA Interface: This interface is used by the database administrator to create databases, Users, to set system parameters for changing database schema etc. Fig. given below shows admin menu where DBA is can create new user and can assign privileges to him.
Graphical User Interface: This interface represents database
Graphical User Interface: This interface represents database
Tuesday, 7 May 2013
Classification of Database Management System
Database Management System can be classified on several DBMS criteria.
A) On the Basis of Data Models.
Data model is a collection of high level data description that hides many low level storage details. A data Model has following three Components:
1) A Structural Part that consist of a set of rules according to which database is constructed.
2) A Manipulating Part That defines type of operations that are allowed on data.
3) A set of integrity rules that ensures that data is correct.
The Data Models are further divided into Three Categories:
1) A Structural Part that consist of a set of rules according to which database is constructed.
2) A Manipulating Part That defines type of operations that are allowed on data.
3) A set of integrity rules that ensures that data is correct.
The Data Models are further divided into Three Categories:
I) Object Base Data Models: Object based data models defines a database in terms of objects, their properties, and their operations .Objects of same behavior and structure belongs to a class and classes are organized into hierarchies. The operations of each class are specified in terms of predefined procedures called methods. Commonly used object based data models are:
Entity Relationship, Object Oriented, Semantic, Functional
II) Physical Data Models: Physical data models include all data artifacts that are
Entity Relationship, Object Oriented, Semantic, Functional
II) Physical Data Models: Physical data models include all data artifacts that are
Sunday, 28 April 2013
DBMS Languages
DBMS Support a variety of users and provides appropriate languages and interface or each category of users.Here are some languages that are provided by DBMS:
1) Data Definition Language (DDL): This Language is used define data structures and specially database schemas. these statements are used to create, alter, or drop data structures. ALTER ,CREATE ,DROP are some examples of DDL.
2) Storage Definition Language (SDL): This language is used to define internal schema. It defines that what will be the Physical structure of database, How many bites per field will be used, what will be the order of fields, and how records will be accesses etc.
3) View Definition Language (VDL): This language is used to specify user views and their mapping to conceptual schema. It defines the subset of records available to classes of users. It creates virtual tables and the view appears to users like conceptual level.It specifies user interfaces.
4) Data Manipulation Language (DML): It is used at conceptual level and external level and is used to perform operations like Query, Delete Update or Insert.Read Only Queries are also sometimes considered as component of DML.It modifies the data but not schema or database objects. These languages are further divided into two types:
1) Data Definition Language (DDL): This Language is used define data structures and specially database schemas. these statements are used to create, alter, or drop data structures. ALTER ,CREATE ,DROP are some examples of DDL.
2) Storage Definition Language (SDL): This language is used to define internal schema. It defines that what will be the Physical structure of database, How many bites per field will be used, what will be the order of fields, and how records will be accesses etc.
3) View Definition Language (VDL): This language is used to specify user views and their mapping to conceptual schema. It defines the subset of records available to classes of users. It creates virtual tables and the view appears to users like conceptual level.It specifies user interfaces.
4) Data Manipulation Language (DML): It is used at conceptual level and external level and is used to perform operations like Query, Delete Update or Insert.Read Only Queries are also sometimes considered as component of DML.It modifies the data but not schema or database objects. These languages are further divided into two types:
Saturday, 30 March 2013
Database Normalization
Database Normalization is the process of organizing data in a database by eliminating redundancy and inconsistent dependency. it divides large tables into smaller tables ,which are less redundant , and defines relationships between them.The Main motive is to isolate data so that additions, deletions, and modifications of a field is made in just one table and then propagated through the rest of the database using the defined relationships.
Database normalization uses few rules . Each rule is called a “normal form.” If the first rule is observed, the database is said to be in “first normal form.” If the first three rules are observed, the database is considered to be in “third normal form.” Although other levels of normalization are possible, third normal form is considered the highest level necessary for most applications.
Database normalization uses few rules . Each rule is called a “normal form.” If the first rule is observed, the database is said to be in “first normal form.” If the first three rules are observed, the database is considered to be in “third normal form.” Although other levels of normalization are possible, third normal form is considered the highest level necessary for most applications.
Normalization Form
|
Description
|
Example
|
First normal
form (1NF) |
It is a property of a relation in a relational database. A relation is in first normal form if the domain of each attribute contains only atomic values, and the value of each attribute contains only a single value from that domain
|
For example, to track an inventory item that may come from two possible sources, an inventory record may contain fields for Vendor Code 1 and Vendor Code 2. |
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