Chapter 9 SQL and RDBMS Part C. SQL Copyright 2005 Radian Publishing Co.

2/26 Contents Chapter 9 SQL and RDBMS 9.1 What is SQL 9.1 A. DDL 9.1 B. DML 9.1 C. DCL 9.2 SQL and RDBMS 9.2 A. MS Access 97, 2003 and Visual FoxPro9.2 A. MS Access 97, 2003 and Visual FoxPro 9.2 B. MySQL9.2 B. MySQL 9.3 Creating a Database 9.4 Creating a Table 9.5 Creating a Table with Constraints 9.6 Filling Table with Data 9.7 Other DDL Commands

Copyright 2005 Radian Publishing Co.3/26 Chapter 9 SQL and RDBMS SQL stands for Structured Query Language. A relational database management system (RDBMS) fully supports SQL.

Copyright 2005 Radian Publishing Co.4/ What is SQL Set-oriented means that SQL processes sets of data in groups. Non-procedural means that SQL does not care about how the result is obtained, but it stresses on what result will be obtained. SQL commands can be classified into three types: Data Definition Language (DDL) commands Data Manipulation Language (DML) commands Data Control Language (DCL) commands

Copyright 2005 Radian Publishing Co.5/ A. DDL Data Definition Language (DDL) commands are used to create, alter and delete tables, views and indexes, including CREATE DATABASE DROP DATABASE CREATE TABLE DROP TABLE ALTER TABLE CREATE INDEX DROP INDEX CREATE VIEW DROP VIEW

Copyright 2005 Radian Publishing Co.6/ B. DML (1/2) Data Manipulation Language (DML) commands are used to update, insert, modify and query the data in the database, including SELECT INSERT UPDATE DELETE

Copyright 2005 Radian Publishing Co.7/ B. DML (2/2) The reasons for writing programs to issue SQL commands are 1.meeting specific needs of an organisation 2.providing interface for users who do not know SQL 3.handling errors 4.enforce database security

Copyright 2005 Radian Publishing Co.8/ C. DCL Data Control Language (DCL) commands help DBA to control and maintain the database, including GRANT, ALTER USER etc. DBA stands for database Administrator (see Chapter 3)

Copyright 2005 Radian Publishing Co.9/ SQL and RDBMS The SQL standards are promoted by two standards organisations: the American National Standards Institute (ANSI) and International Standards Organisation (ISO). In the textbook, ANSI-92 (launched in 1992) will be used. Proprietary Extensions mean including extension to the standards, like ANSI-92.

Copyright 2005 Radian Publishing Co.10/ A. MS Access 97, 2003 and Visual FoxPro MS Access® 97, MS Access® 2003 and MS Visual FoxPro® 5.0 are software products of Microsoft.

Copyright 2005 Radian Publishing Co.11/ B. MySQL MySQL is an open source RDBMS product, meaning that it is possible for anyone to use and modify the software. MySQL always works in the client-server mode, even in a standalone computer. Fig.9.1 Versions of MySQL

Copyright 2005 Radian Publishing Co.12/ Creating a Database (1/2) Fig.9.3 Handling of database files by different DBMS

Copyright 2005 Radian Publishing Co.13/ Creating a Database (2/2) In MS Access, related tables are stored in a single file. In Visual FoxPro, database container is optional. The SQL command to create database: CREATE DATABASE dBName; MySQL command to show database: SHOW DATABASES; MySQL command to open a database: USE dBName;

Copyright 2005 Radian Publishing Co.14/ Creating a Table (1/3) The basic syntax for creating a new table is CREATE TABLE TableName1 (FieldName1 FieldType [(FieldWidth [, Precision])] [NOT NULL] [PRIMARY KEY] [UNIQUE] [, FieldName2...]);

Copyright 2005 Radian Publishing Co.15/ Creating a Table (2/3) Fig.9.4 Table to be created Fig.9.5 Structure of the table to be created

Copyright 2005 Radian Publishing Co.16/ Creating a Table (3/3) The SQL statement for creating the table BRASSITEM

Copyright 2005 Radian Publishing Co.17/ Creating a Table with Constraints (1/2) Some DBMS enforces constraints to insure data integrity. The constraints include 1.the field value is unique (keywords UNIQUE or PRIMARY KEY). 2.the field value is non-empty (keywords NOT NULL or PRIMARY KEY). 3.providing default field value (keyword DEFAULT) 4.generating a number for a numeric field when new record is created (keyword AUTO_INCREMENT) 5.make sure that a foreign key will be updated if the primary key is updated (keyword FOREIGN KEY, CHECK, CASCADE, RESTRICT, ON DELETE and ON UPDATE)

Copyright 2005 Radian Publishing Co.18/ Creating a Table with Constraints (2/2) MySQL command to show the structure of the table: SHOW FIELDS FROM TableName;

Copyright 2005 Radian Publishing Co.19/ Filling Table with Data (1/3) The basic syntax for inserting a new record is: INSERT INTO TableName [(FieldName1 [, FieldName2...])] VALUES (Expression1 [, Expression2...]);

Copyright 2005 Radian Publishing Co.20/ Filling Table with Data (2/3) If all the fields will be filled with values, you may skip entering the field names in the Insert statement.

Copyright 2005 Radian Publishing Co.21/ Filling Table with Data (3/3) The date format in ANSI-92 is YYYY-MM-DD. Dates should be enclosed in quotation marks. For example ' ' represents the 1st day in April of This format applies to MySQL, MS Access 97 and MS Access 2003, but not in Visual FoxPro. In Visual FoxPro, however, the default date format is MM-DD-YYYY, and braces are used instead of quotation marks. For example { }

Copyright 2005 Radian Publishing Co.22/ Other DDL Commands (1/5) The basic syntax for creating an index is: CREATE INDEX IndexName ON TableName (FieldName [ASC|DESC],...);

Copyright 2005 Radian Publishing Co.23/ Other DDL Commands (2/5) The syntax for changing the structure of a table is: ALTER TABLE TableName1 ADD | ALTER (MODIFY|CHANGE) | DROP [COLUMN] FieldName1 FieldType [(FieldWidth [, Precision])];

Copyright 2005 Radian Publishing Co.24/ Other DDL Commands (3/5) In MS Access and FoxPro, ALTER COLUMN is used to change the size and data type of a field. But, you cannot change a field name. In MySQL, MODIFY COLUMN is used to change the size and data type of a field. CHANGE COLUMN is used to change a field name.

Copyright 2005 Radian Publishing Co.25/ Other DDL Commands (4/5) The SQL command to delete a table: DROP TABLE TableName;

Copyright 2005 Radian Publishing Co.26/ Other DDL Commands (5/5) The SQL command to delete database: DROP DATABASE DBName;