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Database Management Using SQL
Professor: Enoch E. Damson
Database Concepts
 A 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
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Database Concepts
 An entity is a distinct object, for example, a person's name, a
product, or an event, to be presented in the table
 The 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 columns
 The rows in the table are called records
 A record contains information about a given entity
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Sample Item Database Table
Item Number
Item Name
Unit Price
Inventory
100
Camera
$267.99
13
101
Washer
$489.56
8
102
TV
$189.99
29
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Creating Tables
 Details required to create database tables include:
Table name
1.

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 types
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Data Types
Data type
Sample data
Description
CHAR(length)
Newcastle
Dr.
For nonnumeric data. Fixed
length
VARCHAR(length)
Newcastle
Dr.
INTEGER
123456
For nonnumeric data. Variable
length (listed length indicates
maximum)
For whole number data between
–231 and +231-1
SMALLINT
31
For whole number data between
–215 and +215-1
NUMERIC
2.6E+10
DATE
11/16/2001
Very large or vary small
numbers
For date. Implementations vary
in different databases
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Primary Key
 An integrity constraint that uses a unique identifier to
uniquely identify a record in a table
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Using Common Fields (Foreign Keys)
to Link Two Tables
productI
D
100
200
productNa
me
Washer
TV
mode
l
D1
S2
manufacturerID
name
1
2
Price
356.9
9
255.6
8
manufacture
rID
1
2
phone
Weiwei Co.
addres
s
Edward
Rd
XYZ Co.
Central
654321
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123456
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An Introduction to SQL
 The Structured Query Language (SQL) is a language embedded
in relational DBMSs to process relational databases
 SQL can be used as a:
Data definition language (DDL):
1.


Used to define a table’s column, add or delete columns, and delete
unneeded tables
Example: Create table, alter table, drop table, etc
Data manipulation language(DML):
2.


Used to insert, update, delete, and retrieve data in a table
Example: Insert into, update, delete, and select
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Creating and Dropping Tables
CREATE TABLE tableName
(field1 dataType, field2 dataType, …)
CREATE TABLE tableName
(field1 dataType PRIMARY KEY,
field2 dataType, …)
DROP TABLE tableName
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Example: Student Table
CREATE TABLE student (
id integer PRIMARY KEY,
firstName varchar(15),
lastName varchar(15));
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Inserting Data Into a Table
INSERT INTO TABLE tableName VALUES (value1, value2, …)
or
INSERT INTO TABLE tableName (field1, field2, …) VALUES (
value1, value2, …)
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Updating Table Data
UPDATE 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
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Updating Table Data
 Conditions 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
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Deleting Records from a Table
 DELETE 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
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Retrieving Data
SELECT field1, field2, …
FROM tableName
WHERE 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
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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
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Wildcard Characters
 Special symbols that represent any character or
combination of characters
 Make it easier to use inexact spelling in a query
 The percent symbol % represents any collection of
characters, including zero characters
 The underscore _ represents any individual character
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Sorting Retrieved Data
SELECT field1, field2, … FROM tableName WHERE
conditions
ORDER BY sort_field1 DESC, sort_field2, …
 Sort data retrieved in a particular order
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Steps to Accessing Databases
1.
2.
3.
4.
5.
6.
7.
Load the database driver
Define the connection URL
Establish the connection
Create the statement object
Execute a query or update
Process the results
Close the connection
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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
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Client-side Scripts and Browser
Dependency
 Client-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
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