Database Programming

DATABASE PROGRAMMINGHenry Osborne

DATABASE

A comprehensive collection of related data organized for convenient access, generally in a computer

RELATIONAL DATABASE

A relational database is a collection of data items organized as a set of formally-described tables from which data can be accessed or reassembled in many different ways without having to reorganize the database tables. The relational database was invented by E. F. Codd at IBM in 1970.

http://searchsqlserver.techtarget.com/definition/relational-database

INDICES

• Make it possible to organize the data in a table according to one or more columns.• One of the cardinal elements of relational databases• Can usually be created on one or more columns of a table• Can also be declared as unique• Primary keys are a special type of unique index that is

used to determine the “natural” method of uniquely identifying a row in a table

RELATIONSHIPS

• One-to-one: at most, one row in the child table can correspond to each row in the parent table

• One-to-many: an arbitrary number of rows in the child table can correspond to any one row in the parent table

• Many-to-many: an arbitrary number of rows in the child table can correspond to an arbitrary number of rows in the parent table

DATA TYPES

int or integer

Signed integer number, 32 bits in length.

smallint Signed integer number, 16 bits in length.real Signed floating-point number, 32 bits in

length.float Signed floating-point number, 64 bits in

length.char Fixed-length character string.varchar Variable-length character string.

CREATING DATABASES

CREATE DATABASE <dbname>;CREATE SCHEMA <dbname>;

CREATE TABLES

CREATE TABLE <tablename> (<col1name> <col1type> [<col1attributes>],[...<colnname> <colntype> [<colnattributes>]]

);

CREATE TABLES

CREATE TABLE book (id INT NOT NULL PRIMARY KEY,isbn VARCHAR(13),title VARCHAR(255),author VARCHAR(255),publisher VARCHAR(255)

);

CREATING INDICES AND RELATIONSHIPS

CREATE INDEX <indexname>ON <tablename> (<column1>[, ..., <columnn>]);

CREATE INDEX book_isbn ON book (isbn);

CREATING INDICES AND RELATIONSHIPS

CREATE TABLE book_chapter (isbn VARCHAR(13) REFERENCES book (id),chapter_number INT NOT NULL,chapter_title VARCHAR(255)

);

DROPPING OBJECTS

DROP TABLE book_chapter;

DROP SCHEMA my_book_database;

ADDING/MANIPULATING DATA

INSERT INTO <tablename> VALUES (<field1value>[, ..., <fieldnvalue>]);

OR

INSERT INTO <tablename>(<field1>[, ..., <fieldn>])VALUES(<field1value>[, ..., <fieldnvalue>]);

ADDING/MANIPULATING DATA

INSERT INTO book (isbn, title, author)VALUES (’0812550706’, ’Ender\’s Game’, ’Orson Scott Card’);

ADDING/MANIPULATING DATA

To update records, you can use the UPDATE statement.

UPDATE bookSET publisher = ’Tor Science Fiction’, author = ’Orson S. Card’WHERE isbn = ’0812550706’;

REMOVE DATA

DELETE FROM book;

DELETE FROM book WHERE isbn = ’0812550706’;

RETRIEVE DATA

SELECT * FROM book;

SELECT * FROM book WHERE author = ’Ray Bradbury’;

SELECT * FROM book

WHERE author = ’Ray Bradbury’ OR author = ’George Orwell’;

SELECT * FROM book

WHERE author = ’Ray Bradbury’ AND publisher LIKE ’%Del Ray’;

SQL JOINS

SELECT *FROM book INNER JOIN book_chapterON book.isbn = book_chapter.isbn;

OUTER JOINS

SELECT book.title, author.last_nameFROM authorLEFT JOIN book ON book.author_id = author.id;

OUTER JOINS

SELECT book.title, author.last_nameFROM authorRIGHT JOIN book ON book.author_id = author.id;

PHP DATA OBJECTS (PDO)

• The standard distribution of PHP 5.1 and greater includes PDO and the drivers for SQLite by default• There are many other database drivers for PDO,

including:• Microsoft SQL Server• Firebird• MySQL• Oracle• PostgreSQL, and• ODBC

PHP DATA OBJECTS (PDO)

•Once installed, the process for using each driver is, for the most part, the same because PDO provides a unified data access layer to each of these database engines.• There is no longer a need for separate mysql_query() or pg_query() functions.• PDO provides a single object-oriented interface to these databases.

DATABASE CONNECTION

$dsn = ’mysql:host=localhost;dbname=library’;$dbh = new PDO($dsn, ’dbuser’, ’dbpass’);

ERROR HANDLING

try {$dsn = ’mysql:host=localhost;dbname=library’;$dbh = new PDO($dsn, ’dbuser’, ’dbpass’);$dbh->setAttribute(PDO::ATTR_EMULATE_PREPARES, TRUE);$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);// All other database calls go here

}

catch (PDOException $e)

{

echo ’Failed: ’ . $e->getMessage();

}

DATABASE QUERY WITH PDO$author = ’’;

if (ctype_alpha($_GET[’author’])){

$author = $_GET[’author’];

}

// Escape the value of $author with quote()

$sql = ’SELECT author.*, book.* FROM author LEFT JOIN book ON author.id = book.author_id WHERE author.last_name = ’ . $dbh->quote($author);

// Execute the statement and echo the results

$results = $dbh->query($sql);

foreach ($results as $row)

{

echo "{$row[’title’]}, {$row[’last_name’]}\n";

}

DATABASE QUERY WITH PDO

$results = $dbh->query($sql);

$results->setFetchMode(PDO::FETCH_OBJ);

foreach ($results as $row)

{

echo "{$row->title}, {$row->last_name}\n";

}

DATABASE QUERY WITH PDO

$sql = "INSERT INTO book (isbn, title, author_id, publisher_id)

VALUES (’0395974682’, ’The Lord of the Rings’, 1, 3)";

$affected = $dbh->exec($sql);

echo "Records affected: {$affected}";

DATABASE PROGRAMMING