SQL Structured Query Language

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 Currency tblCourse Field Name Data Type SizeFormat Key Type IndexRequired courseCodeText8 Primary Key Yes(no duplicates) Yes titleText25Yes costCurrencyCurrencyNo

SQL (Data Definition Language - DDL Database Definition Commands  CREATE DATABASE  DROP DATABASE  SHOW DATABASES  CREATE TABLE  ALTER TABLE

SQL Create Table CREATE TABLE CREATE TABLE (,, ….. ….. );

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.

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

Implementation of a Physical Design StudentCourse(studentID, courseCode) FK studentID → tblStudent Update Cascade, Delete Restrict FK studentID → tblStudent Update Cascade, Delete Restrict FK courseCode → tblcourse 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

SQL Create Table CREATE TABLE tblStudentCourse (studentID VARCHAR(8), (studentID VARCHAR(8), courseCode VARCHAR(8), courseCode VARCHAR(8), PRIMARY KEY (studentID, courseCode) PRIMARY KEY (studentID, courseCode) ); );

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, …)

Adding data using SQL INSERT INTO targetTable (Field1, Field2, …)  VALUES (Value1, Value2, …)

Adding data using SQL Method 1 INSERT INTO tblProduct (prodID, prodDesc, cost) VALUES (‘ssaay1’, ‘Nut’, 34.50)

Adding data using SQL 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’) Adding data using SQL

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

NEXT WEEK Chapter 7 More Advanced SQL Next Week is an in class-Test- Logical Design Test