1. Chapter 22 - SQL, MySQL, DBI and ADO
Outline
Introduction
Relational Database Model
Relational Database Overview
Structured Query Language
Basic SELECT Query
WHERE Clause
GROUP BY Clause
ORDER BY Clause
Merging Data from Multiple Tables
Inserting a Record
Updating a Record
DELETE FROM Statement
TitleAuthor Query from Books.mdb
MySQL

2. Chapter 22 - SQL, MySQL, DBI and ADO
Outline
Introduction to DBI
Perl Database Interface
Python DB-API
PHP dbx module
ActiveX Data Objects (ADO)
Internet and World Wide Web Resources

3. Database management system (DBMS)
22.1 Introduction
Database
Integrated collection of data
Database management system (DBMS)
Provides mechanisms for storing and organizing data
Allows users to access and store data without addressing internal representation of databases
Relational databases
Consist of data corresponding to one another
Most popular database systems in use
Uses Structured Query Language (SQL) to create queries
Examples: Oracle, MS SQL Server, MySQL, Informix

4. 22.2 Relational Database Model
Logical representation of data allowing users to consider relationships between data
Consists of tables
Following figure illustrates Employee table
Might exist in personnel system
Table row called record
Table column called field
Number field is primary key
Contains unique data that cannot be duplicated
Identifies the record
Examples: social security number, employee ID number, etc.

5. 22.2 Relational Database Model
Fig Relational database structure.

6. 22.2 Relational Database Model
SQL statements
Use to obtain table subsets
Complete set of keywords enable programmers to define complex queries
Results of query called result sets (or record sets)
Following table shows results of SQL query (Fig. 22.2)
Provides geographical location of several departments
Fig Result set formed by selecting data from a table.

7. 22.3 Relational Database Overview
Overview SQL using Books.mdb database
Consists of four tables
Authors, Publishers, AuthorISBN and Tables
Primary key fields in italics
Authors table (Figs and 22.4)
Consists of four fields
Unique ID number, first name, last name and year of birth
Contains null value for YearBorn field
Not primary key, so can contain null values
FirstName and LastName can contain null values also

8. 22.3 Relational Database Overview

9. 22.3 Relational Database Overview
Publishers table (Figs and 22.6)
Consists of two fields
Unique ID and publisher name

10. 22.3 Relational Database Overview
Titles table (Figs and 22.8)
Consists of six fields
ISBN number, title, edition number, year published, book description and publisher ID number

11. 22.3 Relational Database Overview

12. 22.3 Relational Database Overview
AuthorISBN table (Figs and 22.10)
Consists of two fields
ISBN number and author ID number
Links names of authors with respective book titles

13. 22.3 Relational Database Overview

14. 22.3 Relational Database Overview
Microsoft Access diagram (Fig )
Illustrates relationships between tables in database
Lines represent table relationships
One-to-many relationship
Example: line between Publishers and Titles tables
Single publisher can have many books in Titles table

15. 22.3 Relational Database Overview
Fig Table relationships in Books.mdb.

16. 22.3 Relational Database Overview
Rule of Entity Integrity
Every record must have value in primary key field
Primary key values must be unique
Foreign key field (or constraints)
References primary key field in another table
Specified when creating tables
Maintains Rule of Referential Integrity
Every foreign key field value must appear in another table’s primary key field
Example: PublisherID field in Titles table
Enables information from multiple tables to be joined for analysis

17. 22.4 Structured Query Language
Overview SQL using Books.mdb database
Following table lists some SQL keywords

18. Extracts information from one or more tables Simplest form
Basic SELECT Query
Extracts information from one or more tables
Simplest form
SELECT * FROM TableName
Asterisk (*) notifies query to select all rows and columns from table
TableName specifies a table in database
Example: SELECT * FROM Authors
Selecting specific fields
Replace asterisk (*) with field names
Example: SELECT AuthorID, LastName FROM Authors

19. Basic SELECT Query

20. Optional clause in SELECT query
WHERE Clause
Optional clause in SELECT query
Selects records satisfying selection criteria
Basic form
SELECT fieldName1, fieldName2 FROM TableName WHERE criteria
Example: SELECT * FROM Authors WHERE YearBorn > 1960
Result set contains two authors born after 1960

21. 22.4.2 WHERE Clause Can contain operators LIKE operator
<, >, <=, >=, =, <> and LIKE
LIKE operator
Performs pattern matching with wildcard characters asterisk (*) and question mark (?)
Pattern matching allows SQL to search for particular string or string of characters
Asterisk (*) indicates string can have zero or more characters at it’s position
Example: SELECT AuthorID, FirstName, LastName, YearBorn FROM Authors WHERE LastName LIKE ‘D*’
Result set contains two records

22. WHERE Clause

23. 22.4.2 WHERE Clause LIKE operator, cont.
Question mark (?) indicates single character can occupy it’s position
Example: SELECT AuthorID, FirstName, LastName, YearBorn FROM Authors WHERE LastName LIKE ‘?i*’
Result set contains one author

24. Specifying range of characters
WHERE Clause
Specifying range of characters
Use [startValue-endValue]
startValue is first character in range
endValue is last character in range

25. Groups result set by a particular column Basic form
GROUP BY Clause
Groups result set by a particular column
Basic form
SELECT fieldName, COUNT(*) FROM TableName GROUP BY fieldName
COUNT returns number of records selected by query
Example: SELECT AuthorID, COUNT (*) AS Count FROM AuthorISBN GROUP BY AuthorID
COUNT (*) AS Count assigns name to column that contains total count values

26. Combining WHERE and GROUP BY clauses
Example: SELECT AuthorID, COUNT(*) AS Count FROM AuthorISBN WHERE AuthorID <= 3 GROUP BY AuthorID
Result set contains three records

27. Sorts result set by given criteria Basic form
ORDER BY Clause
Sorts result set by given criteria
In ascending order (ASC) or descending order (DESC)
Basic form
SELECT fieldName1, fieldName2 FROM TableName ORDER BY fieldName ASC
Can replace ASC with DESC
Example: SELECT AuthorID, FirstName, LastName, YearBorn FROM Authors ORDER BY LastName ASC

28. 22.4.4 ORDER BY Clause Basic form, cont.
To obtain same list in descending order
Example: SELECT AuthorID, FirstName, LastName, YearBorn FROM Authors ORDER BY LastName DESC

29. 22.4.4 ORDER BY Clause Sorts multiple fields
Example: SELECT AuthorID, FirstName, LastName, YearBorn FROM Authors ORDER BY LastName, FirstName
ASC keyword is default sorting order, so is optional
First sorts by last name, then by first name

30. Combining WHERE and ORDER BY clauses
Example: SELECT ISBN, Title, EditionNumber, YearPublished, PublisherID FROM Titles WHERE Title LIKE ‘*How to Program’ ORDER BY Title ASC
Selects titles ending in “How to Program”
Sorts them in ascending order

31. ORDER BY Clause

32. 22.4.5 Merging Data from Multiple Tables
May need to combine data from different tables
Merging data = joining tables
Combines records from different tables
Extracts records common to tables
Basic form
SELECT fieldName1, fieldName2 FROM TableName1, TableName2 WHERE TableName1.fieldName = TableName2.fieldName
WHERE clause specifies fields to be compared from each table
Normally represent primary key field in one table and foreign key field in other table

33. 22.4.5 Merging Data from Multiple Tables
Basic Form, cont.
Example: SELECT FirstName, LastName, ISBN FROM Authors, AuthorISBN WHERE Authors.AuthorID = AuthorISBN.AuthorID ORDER BY LastName, FirstName
Merges FirstName and LastName fields from Authors table with ISBN field from AuthorISBN table
Result set contains list of authors and ISBN numbers of books each author wrote
Sorts in ascending order by LastName and FirstName

34. 22.4.5 Merging Data from Multiple Tables

35. 22.4.5 Merging Data from Multiple Tables
Fully qualified name
TableName.fieldName specifies fields to be compared
Fields with same name in tables require “TableName.” syntax
Cross database queries require database name before TableName

36. Use INSERT INTO operation Basic Form
Inserting a Record
Use INSERT INTO operation
Basic Form
INSERT INTO TableName (fieldName1, fieldName2) VALUES (value1, value2)
TableName specifies table that receives new records
Comma-separated list of field names specify the fields of TableName
Specifies columns that receive new records
VALUES specifies data to be inserted into table
Example: INSERT INTO Authors (FirstName, LastName, YearBorn) VALUES (‘Sue’, ‘Smith’, 1960)
Inserts three values into three columns of Authors table

37. Inserting a Record

38. Modifies data in tables (updates records) Basic form:
Updating a Record
Modifies data in tables (updates records)
Basic form:
UPDATE TableName SET fieldName = value1 WHERE criteria
SET assigns values to certain fields
Example: UPDATE Authors SET YearBorn = ‘1969’ WHERE LastName = ‘Deitel’ AND FirstName = ‘Paul’
AND states all components of selection criteria must be satisfied
Can replace WHERE clause with WHERE AuthorID = 2

39. Updating a Record

40. Removes data from tables Basic form
DELETE FROM Statement
Removes data from tables
Basic form
DELETE FROM TableName WHERE criteria
Example: DELETE FROM Authors WHERE LastName = ‘Smith’ AND FirstName = ‘Sue’
Can replace WHERE clause with WHERE AuthorID = 5

41. 22.4.9 TitleAuthor Query from Books.mdb
Books.mdb contains one predefined query
TitleAuthor
Produces table containing book title, ISBN number, last name, book’s year published and publisher’s name
Figure shows query, Figure shows result set

42. Fully qualified names for clarity
TitleAuthor
1 SELECT Titles.Title, Titles.ISBN, Authors.FirstName,
Authors.LastName, Titles.YearPublished,
Publishers.PublisherName
FROM Publishers, Titles, Authors, AuthorISBN
WHERE Publishers.PublisherID = Titles.PublisherID
AND Authors.AuthorID = AuthorISBN.AuthorID
AND Titles.ISBN = AuthorISBN.ISBN
ORDER BY Titles.Title
Lines 1-3 indicate fields that query selects
Joins tables provided that PublisherID in Publishers table matches PublisherID in Titles table
Combines two preceding result sets on condition that ISBN field in Titles table matches ISBN field in AuthorISBN table
Fig TitleAuthor query from the Books.mdb database.

43. 22.4.9 TitleAuthor Query from Books.mdb

44. Pronounced “My Ess Que Ell” Robust and scalable RDBMS
22.5 MySQL
Pronounced “My Ess Que Ell”
Robust and scalable RDBMS
Multiuser, multithreaded server
Performs multiple commands concurrently
Uses SQL to interact with data
Supports various programming languages
C, C++, Java, Python, Perl, PHP, etc
Supports various operating systems
Windows, Linux and Unix
Access multiple databases with single query

45. Databases part of distributed applications
22.6 Introduction to DBI
Databases part of distributed applications
Divides work across multiple computers
Retrieves result set and displays results
Driver
Helps programs access databases
Each can have different syntax
Each database requires its own driver
Interface
Provides uniform access to all database systems
Database interface
Programmatic library for accessing relational database

46. 22.6.1 Perl Database Interface
Perl DBI
Enables users to access relational databases from Perl programs
Database independent
Most widely used interface in Perl
Uses handles (Fig )
Object-oriented interfaces
Driver handles, database handles, statement handles

47. 22.6.2 Python DB-API Python DB-API
Database application programming interface
Portable across several databases
Consists of Connection and Cursor data objects
Connection data object (Fig )
Accesses database through four methods
Cursor data object (Fig )
Manipulates and retrieves data

48. Python DB-API

49. 22.6.3 PHP dbx module dbx module
Consists of seven functions that interface to database modules
Supports MySQL, PostgreSQL and ODBC databases

50. 22.7 ActiveX Data Objects (ADO)
Microsoft Universal Data Access (UDA)
Supports high-performance data access to relational, non-relational and mainframe data sources
Consists of three primary components
OLE DB
Core of UDA architecture
Provides low-level access to data source
Open Database Connectivity (ODBC)
C programming-language library
Uses SQL to access data
ActiveX Data Objects
Simple object modules
Provide uniform access to data source through OLE DB

51. 22.7 ActiveX Data Objects (ADO)
Fig Microsoft’s UDA architecture.
Fig Portion of the ADO object model.

52. 22.7 ActiveX Data Objects (ADO)
ADO object model
Provides objects and collections
Collections
Containers that hold one or more objects of specific type
Following table lists some ADO objects and collections

53. 22.7 ActiveX Data Objects (ADO)