Mysql DBI

Saturday, April 8, 2023 Dept Of ISE, PESIT 1

MySQL

Mysql

-An open source, fast, easy to use.

-ANSI std.

-can easily be integrated into perl programs by using perl DBI-Data Base Interface module.

DBI is an API that allows perl to connect to & query number of SQL databases.

Ex. MySQL, mSQL,PostgreSQL,Oracle, Sybase, & Informix.


MySQL

Make a connection to MySQL server as the root MySQL user.

$ mysql –u root

* MySQL root is used to administer to

MySQL server only.

Check out whether server is running in background.

We can start the server manually.


MySQL/etc/init.d/mysqld start

Now you can able to connect as

$ mysql –u root

You will get mysql prompt

Mysql> show databases;

Mysql> CREATE DATABASES;

Case insensitive

Usually we use uppercase for key words.

Database is container for tables

Table is collection of rows

Row is collection of fields


Mysql

Mysql> USE database-name;

Mysql> CREATE TABLE studinfo(

lastname CHAR(20),

firstname CHAR(20),

age INT);

DROP table name;

Ls –l /var/lib/mysql

We get all database directories

Ls –l /var/lib/mysql/people

We get table files in that directories


Mysql Data types1. TINYINT -128 to 127(signed)

or 0- 255(unsigned)

2. SMALLINT -32768 to 32767(signed) or

o to 65535(unsigned)

3.MEDIUMINT -8388608 to 8388607 or

0 to 16777215

4. INT or INTEGER -2147483648 to 214783647 or 0 to 4294967295

5. BIGINT = 0 to 18446744073709551615 or -9223372036854775808 to 9223372036854775807


MySQL data types

FLOAT

Double

REAL(same as double)

DECIMAL

NUMERIC(same as decimal)


MySQL data types for DATE

Date YYYY-MM-DD

DATETIME YYYY-MM-DD HH:MM;SS

TIMESTAMP YYYYMMDDHHMMSS, YYMMDDHHMMSS

TIME HH:MM:SS

YEAR YYYY or YY


Other character data typesHave BLOB– Binary Large Object that could hold a variable amount of data.

BLOBs are case sensitive.

VARCHAR variable length string upto 255 chars

TINYBLOB – Maximum length 255 chars

TEXT

BLOB max. length 65535 characters

MEDIUMBLOB OR MEDIUMTEXT –max. 16777215 characters

LONGBLOB OR LONGTEXT – 4294967295 characters


CommandsDescribe command gives the information about the table.

Describe book;

Insert inserts the values into table.

Insert into book values(‘ ‘,’ ‘);

Insert into book(name, usn) values(‘hhh’,’777’);

Select selects the records.

Select * from book order by name;

Select * from book order by name desc;


CommandsUpdate –to change the value of an existing record.

Update book set usn=‘777’ where name=“ccc”;

Update book set sal=sal+10777 where name=“ccc”;

Delete command is used to delete the record from table.


Some administrative detailsRoot is MySQL user.

Change user name to something

This can be done changing the databases and granting the previleges to new user.

Use mysql(existing databases)

Grant select, delete, update, insert on people.* to apache@localhost identified by ‘password’

Here apache is user

Password is password.

People is new database.


Setting password is necessary for the first time\

Now use mysql server as follows

$mysql –u apache –p

Enter the password next.

Change the database using USE people.

Show tables;


DATABASE INDEPENDENT INTERFACEDBI enables one to write programs to automate database maintenance & to write other scripts to interface with MySQLDBI is perl module that provides methods to manipulate SQL databases.With DBI one can connect to a database within a perl script & issue all kinds of queries, including SELECT, INSERT, DELETE.PERL program can be to written to connect to database.CGI script can be written to conect and display database on the browser.


Simple perl program#!/usr/bin/perl –w

use strict;

use DBI;

my $dbh=DBI->

connect(‘DBI:mysql:people’,’apache’,’password’) or die “cannot connect “ . DBI->errstr() ;

print “success connected”;

$dbh->disconnect();


Use DBI method tells perl to use the DBI module. This allows to use all methods for sql queries in this class.

Connect - causes perl to connect to the MySQL database using the perl DBI class.

The first argument to connect method is the database to which you want to connect.


Ex. DBI:mysql:people

DBI module server name

database

‘apache’ – user

‘password’ – password.

If sucsessful returns database handler.

-disconnect to shut down the connection.


#! /usr/bin/perl –w

use DBI;

use strict;

my $d;

$d=DBI->connect(‘DBI:mysql:people’,

’apache’,’password’) or die “cannot connect”.DBI->errstr();

my $sh=$d->prepare(‘SELECT * from book’) or die “can’t prepare”.

$d->errstr();

$sh->execute() or die “can’t execute”.

$sh->errstr();


my($x,$y,$z);

While(($x,$y,$z)=$sh->fetchrow())

{

Print “$x $y $z \n”;

}

$sh->finish();

$d->disconnect();


Prepare method prepares the statement & returns a statement handle object that can be used to execute the query by calling execute method.

One more perl example …


#!/usr/bin/perl –w

use strict; use DBI;

my

$dbh=DBI->connect(‘DBI:mysql:people’,

’apache’,’password’) or die “cannot connect “ . DBI->errstr() ;

print “success connected”;

Print “\n”,”-”x40;

Print “enter name=“; Chomp($x=<STDIN>);

Print “enter address=“;Chomp($y=<STDIN>);

Print “enter author=“; Chomp($z=<STDIN>);


my $sh=$d->prepare(‘INSERT INTO book(fname,lname,auth) values(?,?,?)’) or die “can’t prepare”.

$d->errstr();

$sh->execute($x,$y,$z) or die “can’t execute”. $sh->errstr();

Print “\n”,”-”x40;

Print “record inserted”;

$sh->finish();

$d->disconnect();


Table Joins

Two or more tables can be joined to complete data.

Ex. Tables 1. book 2. address.

SELECT address.city FROM address, book where book.auth =“LAMP” AND

address.name=book.name;


Select address.name, address.zip form address, book where address.age<=50 and address.name=book.auth and address.lanme=book.lname order by book.auth;


Loading and dumping databasesCan load a database or otherwise

execute SQL commands from a file.

Simply put the commands or databases into a file ex. Mystuff.sql and load it in with this command.

$ mysql people < mystuff.sql

We can also dump out a database into a file with this command.

$mysqldump people < entiredb.sql;


Technology

Mysql DBI