MySQL - Università di Enna A.A. 2005-06

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Mysql

Basi di Dati

Universit di Enna A.A. 2005/06


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Intro

MySQL and the MySQL logo are registered trademarks ofMySQL AB (a Swedish company)

The MySQL software delivers a very fast, multi-threaded, multi-user, and robust SQL (Structured Query Language) database

server

The MySQL Web site (http://www.mysql.com/) provides the

latest information about MySQL and MySQL AB

the AB part of the company name is the acronym for theSwedish aktiebolag, orstockcompany
http://www.mysql.com/http://www.mysql.com/http://www.mysql.com/http://www.mysql.com/http://www.mysql.com/http://www.mysql.com/http://www.mysql.com/http://www.mysql.com/


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License

The MySQL software is Dual Licensed

Users can choose to use the MySQL software as an Open

Source product under the terms of the GNU General Public

LicenseUsers can purchase a standard commercial license from

MySQL AB

See http://www.mysql.com/company/legal/licensing/for more information on our licensing policies.
http://www.mysql.com/company/legal/licensing/http://www.mysql.com/company/legal/licensing/http://www.mysql.com/company/legal/licensing/http://www.mysql.com/company/legal/licensing/http://www.mysql.com/company/legal/licensing/http://www.mysql.com/company/legal/licensing/http://www.mysql.com/company/legal/licensing/http://www.mysql.com/company/legal/licensing/


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Documentation

The MySQL Database Software is under constant

development, and the Reference Manual is updated

frequently as well. The most recent version of the

manual is available online in searchable form athttp://dev.mysql.com/doc/

Formats available:

HTML

PDF

CHM
http://dev.mysql.com/doc/http://dev.mysql.com/doc/http://dev.mysql.com/doc/http://dev.mysql.com/doc/http://dev.mysql.com/doc/http://dev.mysql.com/doc/http://dev.mysql.com/doc/http://dev.mysql.com/doc/


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Operating Systems Supported by MySQL

It is possible to port MySQL to all modern systems

that have a C++ compiler and a working

implementation ofPOSIX threads

Thread support is needed for the server. To compileonly the client code, the only requirement is a C++

compiler

We use and develop the software ourselves primarily

on Linux (SuSE and Red Hat), FreeBSD, and Sun

Solaris (Versions 8 and 9)


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Operating Systems Supported by MySQL

MySQL has been reported to compile successfully onthe following operating systems:

AIX 4.x, 5.x

Amiga BSDI 2.x

Digital Unix 4.x

FreeBSD 2.x, 3.x, 4.x

Mac OS X

Windows 9x, Me, NT, 2000, XP, and 2003


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Installing MySQL on Windows

A native Windows version of MySQL has been

available from MySQL AB since version 3.21 and

represents a sizable percentage of the daily

downloads of MySQL

The installer for the Windows version ofMySQL 5.0,

combined with a GUI Configuration Wizard,

automatically installs MySQL, creates an option file,starts the server, and secures the default user accounts


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A copy of the MySQL binary distribution forWindows, which can be downloaded fromhttp://dev.mysql.com/downloads/

You may also have the following optionalrequirements:

If you plan to connect to the MySQL server via ODBC,

you also need a Connector/ODBC driver

If you need tables with a size larger than 4GB, install

MySQL on an NTFS or newer filesystem
http://dev.mysql.com/downloads/http://dev.mysql.com/downloads/http://dev.mysql.com/downloads/http://dev.mysql.com/downloads/http://dev.mysql.com/downloads/http://dev.mysql.com/downloads/http://dev.mysql.com/downloads/http://dev.mysql.com/downloads/


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For MySQL 5.0, there are three installation packagesto choose from when installing MySQL on Windows.The packages are as follows:

Essential package

Complete package

Noinstall archive

The Essentials package is recommended for mostusers



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The following entries are created within the newStart menu section:MySQL Command Line Client : This is a shortcut to the

mysql command-line client and is configured to connect as

the root user. The shortcut prompts for a root user passwordwhen connecting

MySQL Server Instance Config Wizard : This is ashortcut to the MySQL Configuration Wizard. Use thisshortcut to configure a newly installed server, or to re-configure an existing server

MySQL Documentation : This is a link to the MySQLserver documentation that is stored locally in the MySQLserver installation directory. This option is not availablewhen the MySQL server is installed using the Essentialsinstallation package.



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The Main Features of MySQL

Written in C and C++

Tested with a broad range of differentcompilers

Works on many different platforms

Uses GNU Automake, Autoconf, and Libtoolfor portability

APIs for C, C++, Eiffel, Java, Perl, PHP,Python, Ruby, and Tcl are available


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Column Types

Many column types:

signed/unsigned integers 1, 2, 3, 4, and 8 bytes long

FLOAT, DOUBLE

CHAR, VARCHAR

TEXT

BLOB

DATE, TIME, DATETIME, TIMESTAMP, YEARSET, ENUM

Fixed-length and variable-length records


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Statements and Functions

Full operator and function support in the SELECTand WHERE clauses of queries.

Full support for SQL GROUP BY and ORDER BY

clauses. Support for group functions (COUNT(),COUNT(DISTINCT ...), AVG(), STD(), SUM(),MAX(), MIN()

Support for LEFT OUTER JOIN and RIGHT

OUTER JOIN Support for aliases on tables and columns as required

by standard SQL


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Statements and Functions (2)

DELETE, INSERT, REPLACE, and UPDATE return the

number of rows that were changed (affected)

The MySQL-specific SHOW command can be used to

retrieve information about databases, database engines, tables,and indexes. The EXPLAIN command can be used to

determine how the optimizer resolves a query

Function names do not clash with table or column names. For

example, ABSis a valid column name. The only restriction isthat for a function call, no spaces are allowed between the

function name and the ( that follows it

You can mix tables from different databases in the same query


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Limits

Handles large databases.

We use MySQL Server with databases that

contain 50 million records We also know of users who use MySQL

Server with 60,000 tables and about 5,000,000,000

rows


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Connectivity

Clients can connect to the MySQL server usingTCP/IP sockets on any platform

The Connector/ODBC (MyODBC) interface provides

MySQL support for client programs that use ODBC(Open Database Connectivity) connections.

For example, you can use MS Access to connect to yourMySQL server.

The Connector/J interface provides MySQLsupport for Java client programs that useJDBC connections


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How Big MySQL Tables Can Be

MySQL 3.22 had a 4GB (4 gigabyte) limit on table

size.

With the MyISAM storage engine in MySQL 3.23,

the maximum table size was increased to 65536terabytes (25671 bytes).

With this larger allowed table size, the maximum

effective table size for MySQL databases is usually

determined by operating system constraints on file

sizes, not by MySQL internal limits


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The following table lists some examples of operatingsystem file-size limits. This is only a rough guide andis not intended to be definitive

Win32 (FAT/FAT32) 2GB/4GB Win32 (NTFS) 2TB

Linux 2.2-Intel 2GB

Linux 2.4+ (ext3) 4TB

Windows users please note: FAT and VFAT (FAT32)are not considered suitable for production use withMySQL. Use NTFS instead

How Big MySQL Tables Can Be


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Connecting to and Disconnecting from

the Server

To connect to the server, you will usually need to

provide a MySQL username when you invoke mysql

and, most likely, a password. If the server runs on a

machine other than the one where you log in, you willalso need to specify a hostname

shell> mysql -h host-u userp

Enter password: ********


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the Server

shell> mysql -h host-u userp

Enter password: ********

host and user represent the hostname where your

MySQL server is running and the username of your

MySQL account

The ******** represents your password; enter itwhen mysql displays the Enter password: prompt.


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the Server


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the Server

Some MySQL installations allow users to connect asthe anonymous (unnamed) user to the server runningon the local host.

If this is the case on your machine, you should beable to connect to that server by invoking mysqlwithout any options:

shell> mysql


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the Server

After you have connected successfully, you can

disconnect any time by typing QUIT (or EXIT) at

the mysql > prompt:

shell> QUIT

Bye

shell> EXIT

Bye

On Unix, you can also disconnect by pressing Control-D


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Entering Queries

mysql> SELECT VERSION( ), CURRENT_DATE;


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Notes When you issue a command, mysql sends it to the

server for execution and displays the results, thenprints another mysql> prompt to indicate that it is

ready for another command.


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Notes (2)

mysql displays query output in tabular form (rows

and columns). The first row contains labels for thecolumns. The rows following are the query results.


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Notes (3)

mysql shows how many rows were returned and how

long the query took to execute, which gives you arough idea of server performance


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Entering Queries

Keywords may be entered in any lettercase. The

following queries are equivalent:

mysql> SELECT VERSION(), CURRENT_DATE;

mysql> select version(), current_date;

mysql> SeLeCt vErSiOn(), current_DATE;


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You can even enter multiple statements on a singleline. Just end each one with a semicolon

Entering Queries


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A command need not be given all on a single line, so

lengthy commands that require several lines are not a

problem

mysql determines where your statement ends by

looking for the terminating semicolon, not by looking

for the end of the input line

Entering Queries


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Entering Queries


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The following table shows each of the prompts you may

see and summarizes what they mean about the state that

mysql is in:

mysql>Ready for new command.->Waiting for next line of multiple-line command

>Waiting for next line, waiting for completion of

a string that began with a single quote (')

Entering Queries


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"> Waiting for next line, waiting for completion of a

string that began with a double quote (")

`> Waiting for next line, waiting for completion of an

identifier that began with a backtick(`)

/*> Waiting for next line, waiting for completion of a comment

that began with /*

Entering Queries


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Entering Queries


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Entering Queries

mysql> SELECT * FROM my_table WHERE name = 'Smith AND age < 30;

'>


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Creating and Using a Database

This section shows you how to:

Create a database

Create a table

Load data into the table

Retrieve data from the table in various ways

Use multiple tables


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Use the SHOW statement to find out what databasescurrently exist on the server



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If the test database exists, try to access it



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USE

USE, like QUIT, does not require a semicolon

You can terminate such statements with asemicolon if you like; it does no harm

It must be given on a single line



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Creating and Selecting a Database

If the administrator creates your database for you when settingup your permissions, you can begin using it. Otherwise, you

need to create it yourself


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Creating and Selecting a Database


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Creating a Table

Creating the database is the easy part, but at this pointit's empty, as SHOW TABLES tells you:


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Creating a Table

Creating the database is the easy part, but at this pointit's empty, as SHOW TABLES tells you:


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Creating a Table

Create table slides (id integer, contents varchar(30), images char);


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Creating a Table

mysql> show tables;


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Creating a Table

mysql> describe slides;


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Loading Data into a Table

After creating your table, you need to populate it. The

LOAD DATA statement is useful for this

Because you are beginning with an empty table, an

easy way to populate it is to create a text file

containing a row for each of your slide, then load the

contents of the file into the table with a singlestatement


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mysql> LOAD DATA LOCAL INFILE- > 'C:\\Documents and Settings\\User\\Documenti\\Didattica\\ceri\\Mysql\\dati\\

> slides.txt' INTO TABLE slides;