Www.hope.ac.uk Deanery of Business & Computer Sciences SQL Structured Query Language Implementation...

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SQL Structured Query Language

Implementation Lecture – 8

Database Technology Level I

2 www.hope.ac.uk Deanery of Business & Computer Sciences

Aims

To introduce the implementation of a Physical design using SQL.

To introduce SQL Data Definition Language (DDL).

To introduce SQL Data Manipulation Language (DML).


Implementation of a Physical Design

Database Design Language Course (courseCode, title, cost)Entity Course is converted to the following physical design. courseCode and title are set to text and indexed appropriately, cost

is set to CurrencytblCourse

Field Name Data Type Size Format Key Type Index Required

courseCode Text 8 Primary Key Yes(no duplicates) Yes

title Text 25 Yes

cost Currency Currency No


SQL (Data Definition Language - DDL

Database Definition Commands CREATE DATABASE DROP DATABASE SHOW DATABASES CREATE TABLE ALTER TABLE


SQL Create Table

CREATE TABLE <table name>

(

<Column Name> <Data Type> <Conditional Clauses> ,

<Column Name> <Data Type> <Conditional Clauses> ,

…..

);


SQL Create Table

Each column definition has 3 components.

<COLUMN NAME> this the name of the attribute identified in the design.

<DATA TYPE> specified for the attribute in the Physical design. The data types available for use will depend on those appropriate for the software with which the database is to be implemented.

<CONDITIONAL CLAUSES> such as specification of Primary Keys, Indexes and Nulls.


SQL Create Table

CREATE TABLE tblCourse (courseCode VARCHAR(8) PRIMARY KEY, title VARCHAR(25) NOT NULL, cost CURRENCY );


Implementation of a Physical Design

StudentCourse(studentID, courseCode) FK studentID→tblStudent Update Cascade, Delete Restrict FK courseCode→tblcourse Update Cascade, Delete Restrict

Entity StudentCourse is converted to the following physical design.

This entity has a Compound Key, all elements of the compound key are identified. Both attributes are foreign keys. This means that their data type and size must exactly

match the data type and the field to which they will be linking to enforce the relationship between the tables.

Compound keys are always indexed yes (duplicates OK)

Field Name Data Type Size Format Key Type Index Required

studentID Text 8 Compound Key Yes(duplicates OK) Yes

courseCode Text 8 Compound Key Yes(duplicates OK) Yes


SQL Create Table

CREATE TABLE tblStudentCourse (studentID VARCHAR(8), courseCode VARCHAR(8),

PRIMARY KEY (studentID, courseCode) );

CREATE TABLE tblStudentCourse (studentID TEXT(8), courseCode TEXT(8), PRIMARY KEY (studentID, courseCode) );

ALTERNATIVE


Enforcing Foreign Keys

ALTER TABLE tblStudentCourse

ADD CONSTRAINT courseStudentCourseFK FOREIGN KEY (courseCode)

REFERENCES tblcourse (courseCode);


Adding data using SQL

INSERT INTO targetTable (Field1, Field2, …) VALUES (Value1, Value2, …)



Method 1

INSERT INTO tblProduct (prodID, prodDesc, cost)

VALUES (‘ssaay1’, ‘Nut’, 34.50)



Method 2

INSERT INTO tblProduct

VALUES (‘ssaay2’, ‘screw’, 4.50);


INSERT INTO tblSupplier

(suppName, suppAdd1, suppAdd2, suppPostCode)

VALUES

(‘Johnsons’, ‘34 Meols Parade’, ‘Meols’, ‘CH47 6AY’)



Summary

Implementation of a Physical Design Use of SQL Create Table Use of SQL Alter Table to enforce foreign

keys. Student individual work Rest of chapter 6


REMEMBER

Implementation Test (3), W/B

18th February 2008 (20%)

Group Work Implementation Due 7th March 2008

Www.hope.ac.uk Deanery of Business & Computer Sciences SQL Structured Query Language Implementation...

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