SQL (Structured Query Language)

The SQL is stand for Structured Query Language. It was originally developed as the query language of the system-R relational at IBM. It becomes the most common languare used for creating, manipulating and querying relational DBMS. There is a need for standard official SQL because many vendors sell SQL products and this new model allows users to measure a given seller’s vision of SQL for completeness. Also it allows users to differentiate SQL features specific to one product from other standard. "The SQL language standard uses the word table to denote relation. To subset of SQL that supports the creation, deletion, and modification on tables is called the Data Definition Language (DDL). For example to create table statement for students's used to define a new table." (pg.62, Ramakrishnan, Gehrke) The sample SQL statement would be following:

CREAT TABLE Students
(sid CHAR (20),
name CHAR (30),
login CHAR (20),
age INTEGER
GPA REAL)

Above information inserted in SQL by using the INSERT command. Students table statements write like the following:

INSERT
INTO Students (sid, name, login, age, GPA)
VALUES (53688, `Smith`, `smith@ee`, 18, 3.2)

Then Students' table show like the following;

sid name login age GPA

53688 Smith smith@ee 18 3.2

Writing SQL statements needs time and practice, especially when you complex databases with many entities and queries.

Resources: Database Management Systems, 3rd Edition, by Ramakrishnan & Gehrke and Information Systems Today, 2nd Edition, by Jessup, Valacich & Wade

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more infor visit: http://www.w3schools.com/SQL/sql_intro.asp

Metadata

Metadata is "data about other data". It describes, explains, locates, make it easier to retrieve, use and manage an information resource. The purpose of the metadata is used to facilitate the understanding, characteristics, and management usage of data. The metadata required for effective data management that varies with different type of data and context. It makes sure that resources will survive and continue to accessiable into the future. (pg.1,NISO)

An item of metadata can describe an individual item or collection of data such as multiple content items and hierarchical levels. "In data processing, metadata is definitional data that provides information about or documentation of other data managed within an application or environment. For example, metadata would document data about data elements or attributes, (name, size, data type, etc) and data about records or data structures (length, fields, columns, etc) and data about data (where it is located, how it is associated, ownership, etc.). Metadata may include descriptive information about the context, quality and condition, or characteristics of the data. It may be recorded with high or low granularity. " (wikipedia.org)

Few Examples of Metadata

A book is one of the example of metadata. The title of the book, author, subject, identifier, number of pages, text and date of publication are metadata.

Photograph is another example of metadata. The date, time and other details that appear on a photo or camera settings are metadata.

References:

wikipedia.org and Understanding Metadata, Published by NISO

figure from:

http://www.fao.org/aims/img/metadata_element_set.jpg

more infor visit:

http://www.library.uq.edu.au/iad/ctmeta4.html

DBMS Architectures

A database management system builds with four compenents. There are modeling language, data structure, database query language and transaction mechanism. "A data model is a map or diagram that represent entities and their relationshiops." (pg.81, Jessup, Valacich & Wade) It has four types of organizations, there are hierarchical model, network model, relational model and object model. According to database model a data modeling language is a schema of each database. A DBMS gives one or more of the four data model and its optimal structure depend on the application's data and applicaton's requirements. Data structures are fields, records, files and objects that is designed to handle a large collection of data stored on a permanent data storage device.

A database query language is a report writer which allow the users to work toghether with database, analyze its data and update its data with the users privileges. So security of the database is proctected and prevents unauthorized users from viewing the confidential information. Users have their own passoward to access to the entire database or subschemas. "For example, an employee database can contain all the data about an individual employee, but one group of users may be authorized to view only payroll data, while others are allowed access to only work history and medical data." (wikipedia.org) A database transaction mechanism is make sure the order of data integrity and faults. It also maintains the integrity of the database. This system protects the records from coloning. For example, only one studendt identification number for one student. No two students with the same student ID number. This specific ID number called unique key in database and each record of an entity must have one unique key in order distinguish between records.

DBMS Softwares

1. DataEase: DataEase is data-intensive software applications for personal computers. It was created by software develpers Arun Gupta and Joseph Busch in 1980. There are two different product in DataEase: DataEase for DOS and DataEase for Windows.

2. ADABAS: ADABAS is a software AG’s primary database management system and it provides an efficient access to data and maintaining the integrity of the database. It is an application that needs very high volumes of data processing and high transaction processing environments.

3. Microsoft Office Access: Access is a relational database management system from Microsoft and software development tools. It stores data in its own format based on the access jet database engine.

Reference: wikipedia.org and garret.ru/goods.html

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more infor visit: http://www.doeacc.edu.in/jsp/syllabus/pdf/a7.pdf

Adavantages of DBMS

Data Independence: Hides details information and provides an abstract. For example, before a buyer shop for books online it gives brief story about that book.

Access to Efficient Data: A DBMS uses a variety of complicated techniques to store and retrieve data efficiently. For example, publisher know immediate result soon his book sold in a retailer.

Data Integrity & Security: DBMS can impose integrity constraints. For example, "before interesting salary information for an employee, the system can check that the department budget is not exceeded. Also, it can enforce access controls that govern what data is visible to different classes of users." (pg.9, Ramarkrishnan, Gehrke)

Data Administration: When many users use the data, the central administration data offer great enhancements.

Concurrent Access & Crash Recovery: Systems protects users from the effect of the failures.

Reduced Application Development Time: System supports important functions that one common to many applications accessing data in the DBMS.

Resources: Database Management Systems, 3rd Edition, by Ramakrishnan & Gehrke and Information Systems Today, 2nd Edition, by Jessup, Valacich & Wade.

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more infor visit:http://www.wisegeek.com/what-is-a-database-management-system.htm

Introduction & History

A Database Management Systems (DBMSs) is a

computer software deliberated to store large

collection of data that manages databases.

In the earliest days of computers, data have been a major application focus when comes to storing and manipulating large collection of data. The general purpose of DBMS in the early 1960s was to integrated data store. In the late 1960s, IBM developed the Information Management System (IMS). IMS created the "basis for an alternative data representation framework called the hierarchical data model." (pg.6, Ramakrishnan, Gehrke)

In 1970, the Relational Data Model (RDM) introduced by IBM. It glowed the rapid development of several DBMS and it dominated its position until 1980s. In the late 1980s and the 1990s, many advance changes made to database systems. "Considerable research was carried out into more powerful query language and richer data models, with emphasis placed on supporting complex analysis of data from all parts of enterprise. The data is stored in a relational DBMS and the application layer can be customized to different companies, leading to lower overall costs for the companies, compared to the cost of building the application layer from scratch." (pg.7,Ramakrishnan, Gehrke)

Lately, the DBMS introduced to the Internet because database gave widespread access to a browser to use the data. "Today the field is being driven by exciting visions such as multimedia database, interactive video, streaming data, digital libraries, a host of scientific projects etc. DBMS represents one of the largest and most vigorous market segments." (pg.7, Ramakrishnan, Gehrke)

FILE SYSTEM VS DBMS

* Data stored in devices (ex: disk, tape)

* Write special programs to answere each question a user may want to ask about the data

* Make sure the data is restored by the new changes or system crashes

1. Designed to make the hard tasks easier

2. Storing data in a DBMS rather than as a collection of operating systems files

3. Manage the data efficient and dynamic

Resources:Database Management System, 3rd Edition, by Ramkrishnan, Gehrke and Wikipedia.com

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more infor visit: http://www.webopedia.com/TERM/D/database_management_system_DBMS.html