programming mysql, perl coen 351. reading list paul dubois: mysql and perl for the web, new riders,...

Programming MySQL, Perl

COEN 351

Reading List

Paul DuBois: MySQL and Perl for the Web, New Riders, 2002

Jacqueline D. Hamilton: CGI Programming 101, 2004

Checking Your Installation

Use this script to check whether cgi and dbi are installed:

You should see mysql among the output.

#! c:/Perl/bin/perl.exe

use CGI;use DBI;$cgi=new CGI;print "CGI object was successfully created\n";@driverNames = DBI->available_drivers();print "These drivers are available: @driverNames\n";exit(0);

Connecting to the Database

Create database and table In MySQL command line:

CREATE DATABASE example1; USE example1; CREATE TABLE nlwest(name varchar(20), wins int, losses int);

SHOW TABLES; DESCRIBE nlwest;

INSERT INTO nlwest VALUES ('Los Angeles',13,8), ('San Francisco', 11, 8), ('San Diego',12,9), ('Arizona', 11, 11), ('Colorado', 9, 13); SELECT * FROM nlwest;

http://dev.mysql.com/doc/refman/5.0/en/

Connecting to the Database#! c:/perl/bin/perl.exeuse strict;use DBI;

my $dbh = DBI->connect ("DBI:mysql:host=localhost;database=example1",

"root", "none");my $sth = $dbh->prepare("SELECT name, wins, losses FROM nlwest");$sth->execute();my $count=0;while( my @val = $sth->fetchrow_array ()) {

printf("name = %s, wins = %d, losses = %d\n",$val[0], $val[1], $val[2]);

$count++;}print "$count teams total\n";$sth->finish();$dbh->disconnect();

DBI Class Method connect

$dbh = DBI->connect($data_source, $username, $password) or die $DBI::errstr;

$dbh = DBI->connect($data_source, $username, $password, \%attr) or die $DBI::errstr;

http://search.cpan.org/~timb/DBI-1.42/DBI.pm#THE_DBI_PACKAGE_AND_CLASS






DBI Class Method prepare

$sth = $dbh->prepare($statement) or die $dbh->errstr; $sth = $dbh->prepare($statement, \%attr) or die $dbh->errstr;

Prepares a statement for later execution by the database engine and returns a reference to a statement handle object.






DBI Class Method execute

$rv = $sth->execute or die $sth->errstr; $rv = $sth->execute(@bind_values) or die $sth->errstr;

Perform whatever processing is necessary to execute the prepared statement.






DBI Class Method fetchrow_array ()

$ary_ref = $sth->fetchrow_arrayref; $ary_ref = $sth->fetch; # alias

Fetches the next row of data and returns a reference to an array holding the field values. Null fields are returned as undef values in the array.






DBI Class Method disconnect

$rc = $dbh->disconnect or warn $dbh->errstr;

Disconnects the database from the database handle. disconnect is typically only used before exiting the program. The handle is of little use after disconnecting.

Sample Script

Alternative Row Retrieval Methods

fetchrow_array()Returns an array

fetchrow_arrayref()Returns a reference to an array

fetchrow_hashref()Returns a reference to an hash

Alternative Row Retrieval Methods#! c:/perl/bin/perl.exeuse strict;use DBI;use CGI qw(:standard :html3);

print header(), start_html("MLB");my $dbh = DBI->connect ("DBI:mysql:host=localhost;database=example1",

"root", "none");my $sth = $dbh->prepare("SELECT name, wins, losses FROM nlwest");$sth->execute();

my @headings = ('Team','Wins','Losses');my @rows = th(\@headings);

while( my @val = $sth->fetchrow_array ()) {push(@rows,td([$val[0],$val[1],$val[2]]));

}print table({-width=>'50%', -align=>'center'},caption(b('NL WEST')),

Tr(\@rows));print end_html();$sth->finish();$dbh->disconnect();

fetchrow_array ()

returns an array





while( my $ref = $sth->fetchrow_arrayref ()) {push(@rows,td([$ref->[0],$ref->[1],$ref->[2]]));



fetchrow_arrayref()

returns reference to an array





while( my $ref = $sth->fetchrow_hashref()) {push(@rows,td([$ref->{name}, $ref->{wins}, $ref->{losses}]));



fetchrow_hashref ()

returns reference to an hash

Letter-Case Variation#! c:/perl/bin/perl.exeuse strict;use DBI;use CGI qw(:standard :html3);


"root", "none",{PrintError => 0, RaiseError => 1} );my $sth = $dbh->prepare("SELECT name, wins, losses FROM nlwest");$sth->execute();


while( my $ref = $sth->fetchrow_hashref( 'NAME_lc')) {push(@rows,td([$ref->{name}, $ref->{wins}, $ref->{losses}]));



MySQL is not case specific, but Perl is.

When using field names, this parameter forces the names to be lower case.

Use NAME-uc to force the names to be upper case.

High-Level Retrieval Methods

Low level access usesprepare()execute() fetch loop finish()

New versions of DBI have

High-Level Retrieval Methods#! c:/perl/bin/perl.exeuse strict;use DBI;use CGI qw(:standard :html3);


"root", "none",{PrintError => 0, RaiseError => 1} ) or die "error";my @row = $dbh->selectrow_array("SELECT name, wins, losses FROM nlwest");print "The leader is $row[0]" if @row;print end_html();$dbh->disconnect();

selectrow_array returns a complete row in a Perl row context.

selectrow_array returns the first column value in a Perl scalar context.



"root", "none",{PrintError => 0, RaiseError => 1} ) or die "error";my $ref = $dbh->selectcol_arrayref ("SELECT name FROM nlwest");print "The teams in order are @{$ref}\n" if defined ($ref);print end_html();$dbh->disconnect();

selectcol_arrayref returns a complete column in a Perl row context.

If the query has no result, it returns an empty list or ‘undef’



"root", "none",{PrintError => 0, RaiseError => 1} ) or die "error";my $ref = $dbh->selectall_arrayref("SELECT name, wins, losses FROM nlwest");my @headings = ('Team','Wins','Losses');my @rows = th(\@headings);foreach my $row_ref (@{$ref}) {

push(@rows,td([$row_ref->[0], $row_ref->[1], $row_ref->[2] ]));}print table({-border=>'1', -width=>'50%', -align=>'center'},caption(b('NL WEST')),

Tr(\@rows) );

print end_html();$dbh->disconnect(); selectall_arrayref returns all values as a matrix.

All methods die if “RaiseError” is enabled

Modifying the database

do() To issue a query that does not return rows

do() returns number of rows affected or undef for an error. If RaiseError is enabled, you do not need to

check

Modifying the database#! c:/perl/bin/perl.exeuse strict;use DBI;use CGI qw(:standard :html3);


"root", "none",{PrintError => 0, RaiseError => 1} ) or die "error";$dbh->do ("INSERT INTO nlwest (name, wins, losses)

VALUES('San Francisco',12,8)" );my $ref = $dbh->selectall_arrayref("SELECT name, wins, losses FROM nlwest");my @headings = ('Team','Wins','Losses');my @rows = th(\@headings);foreach my $row_ref (@{$ref}) {

push(@rows,td([$row_ref->[0], $row_ref->[1], $row_ref->[2] ]));}print table({-border=>'1', -width=>'50%', -align=>'center'},caption(b('NL WEST')),

Tr(\@rows) );

print end_html();$dbh->disconnect();

do() to insert a row

Modifying the databaseuse DBI;use CGI qw(:standard :html3);

sub updateWinsAndLosses{

my ($dbh, $winner, $looser) = @_;$dbh->do ( "UPDATE nlwest SET wins = wins + 1 WHERE name = ?", undef, $winner);$dbh->do ( " UPDATE nlwest SET losses = losses + 1 WHERE name = ?",

undef, $looser);}


"root", "none",{PrintError => 0, RaiseError => 1} ) or die "error";&updateWinsAndLosses($dbh, 'San Francisco', 'Los Angeles');my $ref = $dbh->selectall_arrayref("SELECT name, wins, losses FROM nlwest");my @headings = ('Team','Wins','Losses');my @rows = th(\@headings);foreach my $row_ref (@{$ref}) {

push(@rows,td([$row_ref->[0], $row_ref->[1], $row_ref->[2] ]));}

do() to change values

programming mysql, perl coen 351. reading list paul dubois: mysql and perl for the web, new riders,...

Documents

strict use dbi

use cgi use dbi

dbi class method fetchrow

count teams totaln

database example1 use

losses int

programming mysql

errstr http