2440: 141 web site administration database management using sql professor: enoch e. damson
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The University of AkronCollege of Applied Science & Technology
Dept. of Business & Information Technology
2440: 141Web Site Administration
Database Management Using SQLProfessor: Enoch E. Damson
Database ConceptsA database is a collection of data about an entities
For example, a database might contain checking account information in a bank, product items information in an on-line store, students’ records in a college, and so on
Relational databases store information in simple structures called tables
Most commercial databases today are relational databases
Introduction to SQL 2
Database ConceptsAn entity is a distinct object, for example, a person's name, a
product, or an event, to be presented in the tableThe columns in the table contain fields
A field contains a single, specific piece of information within a record. So, a record is a group of related fields
The data in a table is organized into rows and columnsThe rows in the table are called records
A record contains information about a given entity
Introduction to SQL 3
Sample Item Database Table
Introduction to SQL 4
Item Number Item Name Unit Price Inventory
100 Camera $267.99 13
101 Washer $489.56 8
102 TV $189.99 29
Creating TablesDetails required to create database tables include:
1. Table name
The table name identifies the table
A database can consist of many tables
You use the name of a table to reference the table and to manipulate data in that table
2. Fields names
3. Field data typesIntroduction to SQL 5
Data Types
Introduction to SQL 6
Data type Sample data Description
CHAR(length) Newcastle Dr.
For nonnumeric data. Fixed length
VARCHAR(length) Newcastle Dr.
For nonnumeric data. Variable length (listed length indicates maximum)
INTEGER 123456 For whole number data between –231 and +231-1
SMALLINT 31 For whole number data between –215 and +215-1
NUMERIC 2.6E+10 Very large or vary small numbers
DATE 11/16/2001 For date. Implementations vary in different databases
Primary KeyAn integrity constraint that uses a unique identifier to
uniquely identify a record in a table
Introduction to SQL 7
Using Common Fields (Foreign Keys)to Link Two Tables
Introduction to SQL 8
productID
productName
model
Price manufacturerID
100 Washer D1 356.99
1
200 TV S2 255.68
2
manufacturerID name address
phone
1 Weiwei Co. Edward Rd
123456
2 XYZ Co. Central 654321
An Introduction to SQLThe Structured Query Language (SQL) is a language embedded
in relational DBMSs to process relational databasesSQL can be used as a:
1. Data definition language (DDL): Used to define a table’s column, add or delete columns, and delete
unneeded tables Example: Create table, alter table, drop table, etc
2. Data manipulation language(DML): Used to insert, update, delete, and retrieve data in a table Example: Insert into, update, delete, and select
Introduction to SQL 9
Creating and Dropping TablesCREATE TABLE tableName (field1 dataType, field2 dataType, …) CREATE TABLE tableName
(field1 dataType PRIMARY KEY, field2 dataType, …) DROP TABLE tableName
Introduction to SQL 10
Example: Student TableCREATE TABLE student (
id integer PRIMARY KEY, firstName varchar(15),lastName varchar(15));
Introduction to SQL 11
Inserting Data Into a TableINSERT INTO TABLE tableName VALUES (value1, value2, …)
or
INSERT INTO TABLE tableName (field1, field2, …) VALUES
( value1, value2, …)
Introduction to SQL 12
Updating Table DataUPDATE tableName SET field1=value1, fiedl2=value2, … WHERE conditions
The WHERE clause gives the condition for selecting which rows (records) are to be updated in the table identified as tableName
The SET keyword is followed by the field list to be updated
If the WHERE clause is omitted, all rows in the table are updated
Introduction to SQL 13
Updating Table DataConditions in a WHERE clause are similar to conditional
statements in JSP
Conditions can be constructed with comparison operators and logical operators
You can use the six comparison operators ( =, <> for not equal, <, >, <=, >=) as well as the three logical operators (AND, OR, and NOT) to create compound conditions or to negate a condition
Introduction to SQL 14
Deleting Records from a TableDELETE FROM tableName WHERE conditions
This deletes all rows that satisfy the WHERE clause in the statement
If there is no WHERE clause, then all rows in the table are deleted
Introduction to SQL 15
Retrieving Data
SELECT field1, field2, …FROM tableNameWHERE conditions
The SELECT clause lists the fields retrieved in the query result, separated by commas
The FROM clause lists one or more table names to be used by the query
All fields listed in the SELECT or WHERE clauses must be found in one and only one of the tables listed in the FROM clause
Introduction to SQL 16
Retrieving Data…
The WHERE clause contains conditions for selecting rows from the tables listed in the FROM clause
The data retrieved are from the rows that satisfy the condition (and are therefore selected)
If the WHERE clause is omitted, all rows are selected
Introduction to SQL 17
Wildcard CharactersSpecial symbols that represent any character or
combination of charactersMake it easier to use inexact spelling in a queryThe percent symbol % represents any collection of
characters, including zero charactersThe underscore _ represents any individual character
Introduction to SQL 18
Sorting Retrieved DataSELECT field1, field2, … FROM tableName WHERE
conditions
ORDER BY sort_field1 DESC, sort_field2, …
Sort data retrieved in a particular order
Introduction to SQL 19
Steps to Accessing Databases1. Load the database driver2. Define the connection URL3. Establish the connection4. Create the statement object5. Execute a query or update6. Process the results7. Close the connection
Introduction to SQL 20
Loading a DBMS Driver The DBMS driver acts as the bridge between the server-side
programming environment and the database itself
The driver is a piece of software that knows how to talk to the DBMS
To load a driver, all you need to do is to load the appropriate class
Introduction to SQL 21
Client-side Scripts and Browser DependencyClient-side scripts are executed in the client browser
The browser must provide an appropriate interpreter
All browsers come with built-in engines to support certain client-side scripting languages
Introduction to SQL 22