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DATABASE

Key Issues

What is a database? Some important database concepts and

vocabulary. Key characteristics about the data in a

database.

What is a Database?

Database is a collection of related data that is stored and organized in a manner enabling information to be retrieved from the database as needed.

[Morley 3008 p575]]

Database Software

It is more formally called a database management system (DBMS), is used to create, maintain, and access databases.

A DBMS also controls the organization of the data and protects the integrity and security of the data, so it is accurate and protected against both intentional and accidental damage.

DBMS Product Category

Workgroup/ Personal level Enterprise level

Enterprise level can serve heavier load than personal level in terms of number of users accessing database or amount of data stored in a database.

DBMS Product

Examples of personal level are Microsoft Access, Corel Paradox, Lotus Approach.

Examples of enterprise level are Microsoft SQL Server, Oracle, IBM DB2, MySQL

Database Element

A database typically consists of interrelated tables consisting of fields and records.

A field (column) is a single type of data to be stored in a database, such as Person’s name: Thomas, Jimmy Person’s telephone number: 02-300-4543 ID code: 451277

A record (row) is a collection of related fields.

Key Field

The field which is chosen to be the uniquely identify a record so the record can be easily retrieved and process

Can either called “ ” Eg. Student ID

•David•Thailand•1st Year

David

•David•Australia•2nd Year

David

Student

?•David•Thailand•1st Year

4715233

•David•Australia•2nd Year

4612544

Student

Data Hierarchy

Characters A letter, number or special character Eg. A, B, C, 1, 2, 3, #

Field Unit of data consisting of one or more characters (bytes) Eg. Name, address

Record A collection of related fields Eg. Each student record

Table A collection of related records Eg. Student file

Database An organized collection of integrated files Eg. S&T database

•David•Thailand•1st Year

David

•Annie•Australia•2nd Year

Annie

Student

•Grace•Thailand•CS

Grace

•Peter•Australia•IT

Peter

Teacher

Flat File and Database

Flat File

A file management system is a program that allows the creation of individual database tables (flat files), each of which is stored in its own physical file and is not related to any other file.

Consequently, file management systems can work with only one table at a time, and each table has to contain all the data that may

need to be accessed or retrieved at one time. As a result, file management systems have a

much higher level of redundancy than database management systems.

An organization would have different files for different purposes.

Problem in Flat File Processing Data redundancy Data inaccuracy

Relational Database

In a relational database, data from several tables is tied together (related) using a field that the tables have in common so that information can be extracted from multiple tables, if needed, to fulfill a user request.

File

DB

Advantage of DBMS

Reduced Data Redundancy Data redundancy means the same data fields appear in

many different files and is in different format Save storage space

Improve Data Integrity Data integrity: data is accurate, consistent, and up-to-

date The change of data just make in only one place.

File sharing All authorized users can work on the same set of file.

Increased security Each level of user has different level of access.

Retrieving information from a relational database

Query language

Retrieving data from a database is called query.

Query Language An easy-to-use computer language for making

queries to a database and for retrieving selected records based on criteria.

Query Language

Each DBMS software provides its own tool for query. The most popular is Structured Query Language

Ex. SELECT product_nameFROM product

WHERE price = 100

Form of SQL

The fields used in the query are specified with

The tables to which they belong are specified with

Selection criteria are determined by The query results can be sorted in any

sequence with

Demo

Query/Requirement Retrieve address and e-mail of student ID

5001234

Demo

Query/Requirement Seek the students who get honor.

QBE

• Query By Example(QBE) is a feature of query language that use a sample record form to define the qualifications he wants for selected records. In other words, the user fills in a form

EX

You want to contact to studentID 5201111 So you have to search for E-mail and phone

no. of studentID 5201111.

More SQL Statements

Source : http://www.w3schools.com/sql/sql_quickref.asp

SQL Statement Syntax

AND / OR SELECT column_name(s)FROM table_nameWHERE conditionAND|OR condition

ALTER TABLE ALTER TABLE table_name ADD column_name datatypeorALTER TABLE table_name DROP COLUMN column_name

AS (alias) SELECT column_name AS column_aliasFROM table_nameorSELECT column_nameFROM table_name  AS table_alias

BETWEEN SELECT column_name(s)FROM table_nameWHERE column_nameBETWEEN value1 AND value2

CREATE DATABASE

CREATE DATABASE database_name

CREATE TABLE CREATE TABLE table_name(column_name1 data_type,column_name2 data_type,column_name2 data_type,...)

CREATE INDEX CREATE INDEX index_nameON table_name (column_name)orCREATE UNIQUE INDEX index_nameON table_name (column_name)

CREATE VIEW CREATE VIEW view_name ASSELECT column_name(s)FROM table_nameWHERE condition

DELETE DELETE FROM table_nameWHERE some_column=some_valueorDELETE FROM table_name (Note: Deletes the entire table!!)DELETE * FROM table_name (Note: Deletes the entire table!!)

DROP DATABASE

DROP DATABASE database_name

DROP INDEX DROP INDEX table_name.index_name (SQL Server)DROP INDEX index_name ON table_name (MS Access)DROP INDEX index_name (DB2/Oracle)ALTER TABLE table_nameDROP INDEX index_name (MySQL)

DROP TABLE DROP TABLE table_name

GROUP BY SELECT column_name, aggregate_function(column_name)FROM table_nameWHERE column_name operator valueGROUP BY column_name

HAVING SELECT column_name, aggregate_function(column_name)FROM table_nameWHERE column_name operator valueGROUP BY column_nameHAVING aggregate_function(column_name) operator value

IN SELECT column_name(s)FROM table_nameWHERE column_nameIN (value1,value2,..)

INSERT INTO INSERT INTO table_nameVALUES (value1, value2, value3,....)orINSERT INTO table_name(column1, column2, column3,...)VALUES (value1, value2, value3,....)

INNER JOIN SELECT column_name(s)FROM table_name1INNER JOIN table_name2 ON table_name1.column_name=table_name2.column_name

LEFT JOIN SELECT column_name(s)FROM table_name1LEFT JOIN table_name2 ON table_name1.column_name=table_name2.column_name

RIGHT JOIN SELECT column_name(s)FROM table_name1RIGHT JOIN table_name2 ON table_name1.column_name=table_name2.column_name

FULL JOIN SELECT column_name(s)FROM table_name1FULL JOIN table_name2 ON table_name1.column_name=table_name2.column_name

LIKE SELECT column_name(s)FROM table_nameWHERE column_name LIKE pattern

ORDER BY SELECT column_name(s)FROM table_nameORDER BY column_name [ASC|DESC]

SELECT SELECT column_name(s)FROM table_name

SELECT * SELECT *FROM table_name

SELECT DISTINCT

SELECT DISTINCT column_name(s)FROM table_name

SELECT INTO SELECT *INTO new_table_name [IN externaldatabase]FROM old_table_nameorSELECT column_name(s)INTO new_table_name [IN externaldatabase]FROM old_table_name

SELECT TOP SELECT TOP number|percent column_name(s)FROM table_name

TRUNCATE TABLE

TRUNCATE TABLE table_name

UNION SELECT column_name(s) FROM table_name1UNIONSELECT column_name(s) FROM table_name2

UNION ALL SELECT column_name(s) FROM table_name1UNION ALLSELECT column_name(s) FROM table_name2

UPDATE UPDATE table_nameSET column1=value, column2=value,...WHERE some_column=some_value

WHERE SELECT column_name(s)FROM table_nameWHERE column_name operator value

Master/Transaction fileBatch/Realtime processingIndividual/Distributed databaseDBAData recoveryData mining

Other concepts

Type of Data Files

Master File Data file which contains relatively

permanent records that are generally update periodically

Transaction File Temporary holding file that holds all

change to be made to the master file: addition, deletion, revision.

Each period, master file would be updated with the change called for in transaction file.

Sale Amount

2005Jan45,456 Fab75,558Mar21,794Apr34,129

JanFeb

MarApr

May

Unchanged

update

ProductID

ProductName

Quantity on Hand

001 TV 10

002 Radio 10

003 DVD Player 20

Inventory Table

OrderID CustomerName ProductID Time Quantity

1 Alice 001 11:00 1

OrderID CustomerName ProductID Time Quantity

2 Bob 001 12:00 1

OrderID CustomerName ProductID Time Quantity

3 Charlie 002 17:30 2

Transaction File

Update

Purchase TableMaster File

Batch & Real-time Processing The transactions can be handled via Batch processing (offline processing)

the data is gathered over a period of time and then processed in a set (batch) at periodic intervals, such as at the end of the day or once a week.

Real-time processing (online transaction processing, OLTP) Each transaction is processed immediately

as it is entered.

Database Classification

Single-user vs. Multiuser Database Systems

Centralized vs. Distributed Database Systems

Single-user & Multiuser DB

Single-user Multiuser

Centralized & Distributed DB

Centralized DB Distributed DB

Customer Address

Customer Credit History

Database Administrator (DBA) Person who coordinates all related

activities and needs for an organization’s database.

The DBA determines user access privileges, sets standards, guidelines, and control procedures, backup data.

Responsibilities of DBA Database design, implementation, and operation

How space will be used on secondary-storage devices How file or record may be added, deleted, changed

Coordinate with users User access privileges Control procedures Establish priority for requests Develop user documentation

System security Prevent unauthorized access

Backup and recovery Perform regularly backup Develop plan for recovering data

Performance monitoring Make sure that service for user is at the standard, not too slow

Data Warehouse

It is a comprehensive collection of data about a company and its customers.

In a data warehouse, data from transaction processing and other operations are reorganized and put into a form that is optimized for queries.

http://www.persysinc.com/images/persys_data_warehouse.gif

Data Mining

Data mining makes use of a data warehouse by applying intelligent software to scan its contents for subtle patterns that may not be evident to management.

It identifies patterns and relationships between data. It can be a useful sales and marketing tool to help

retail companies match customers with products that would be likely to purchase – a type of customer profiling.

Wal-Mart is one company that uses extensive data mining and targets specific types of merchandise in their local stores, based on the characteristics of the people that live in that geographical area.

http://www.mbaknol.com/management-information-systems/data-mining-and-its-business-applications/attachment/data-mining/