Deanery of Business & Computer Sciences SQL Structured Query Language Implementation Lecture – 8 Database Technology Level I

Deanery of Business & Computer Sciences 2 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).

Deanery of Business & Computer Sciences 3 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 Currency tblCourse Field NameData TypeSizeFormatKey TypeIndexRequired courseCodeText8Primary KeyYes(no duplicates)Yes titleText25Yes costCurrency No

Deanery of Business & Computer Sciences 4 SQL (Data Definition Language - DDL Database Definition Commands CREATE DATABASE DROP DATABASE SHOW DATABASES CREATE TABLE ALTER TABLE

Deanery of Business & Computer Sciences 5 SQL Create Table CREATE TABLE (, ….. );

Deanery of Business & Computer Sciences 6 SQL Create Table Each column definition has 3 components. this the name of the attribute identified in the design. 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. such as specification of Primary Keys, Indexes and Nulls.

Deanery of Business & Computer Sciences 7 SQL Create Table CREATE TABLE tblCourse (courseCode VARCHAR(8) PRIMARY KEY, title VARCHAR(25) NOT NULL, cost CURRENCY );

Deanery of Business & Computer Sciences 8 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 NameData TypeSizeFormatKey TypeIndexRequired studentIDText8Compound KeyYes(duplicates OK)Yes courseCodeText8Compound KeyYes(duplicates OK)Yes

Deanery of Business & Computer Sciences 9 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

Deanery of Business & Computer Sciences 10 Enforcing Foreign Keys ALTER TABLE tblStudentCourse ADD CONSTRAINT courseStudentCourseFK FOREIGN KEY (courseCode) REFERENCES tblcourse (courseCode);

Deanery of Business & Computer Sciences 11 Adding data using SQL INSERT INTO targetTable (Field1, Field2, …) VALUES (Value1, Value2, …)

Deanery of Business & Computer Sciences 12 Adding data using SQL Method 1 INSERT INTO tblProduct (prodID, prodDesc, cost) VALUES (‘ssaay1’, ‘Nut’, 34.50)

Deanery of Business & Computer Sciences 13 Adding data using SQL Method 2 INSERT INTO tblProduct VALUES (‘ssaay2’, ‘screw’, 4.50);

Deanery of Business & Computer Sciences 14 INSERT INTO tblSupplier (suppName, suppAdd1, suppAdd2, suppPostCode) VALUES (‘Johnsons’, ‘34 Meols Parade’, ‘Meols’, ‘CH47 6AY’) Adding data using SQL

Deanery of Business & Computer Sciences 15 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

Deanery of Business & Computer Sciences 16 REMEMBER Implementation Test (3), W/B 18 th February 2008 (20%) Group Work Implementation Due 7 th March 2008