Display content and its related contents in Perl/Mysql - mysql

Question

I am trying to achieve this sample output from a small Perl project like this
content1
relatedcontent1
relatedcontent2
relatedcontent2
content2
relatedcontent1
relatedcontent2
here is my code
#!C:/Perl64/bin/perl.exe
use strict;
use warnings;
use v5.10; # for say() function
use DBI;
use HTML::Table;
# MySQL database configurations
my $dsn = "DBI:mysql:naxum";
my $username = "root";
my $password = '';
print "Content-Type:text/html\r\n\r\n";
# connect to MySQL database
my %attr = ( PrintError=>0, # turn off error reporting via warn()
RaiseError=>1 # report error via die()
);
my $dbh = DBI->connect($dsn,$username,$password,\%attr);
# query data from the sponsor table
query_sponsor($dbh);
query_person_by_target($dbh);
sub query_sponsor{
# query from the table
my ($dbh) = #_;
my $sql = "SELECT name,id FROM sponsor";
my $sth = $dbh->prepare($sql);
# execute the query
$sth->execute();
print "<table>\n";
print "<thead>\n";
print "<tr>\n";
print "<th>Id</th>\n";
print "<th>Name</th>\n";
print "</tr>\n";
print "</thead>\n";
print "<tbody>\n";
while(my #row = $sth->fetchrow_array()){
print "<tr>\n";
print "<td>\n";
print $row['1'];
sub query_person_by_target{
my ($dbhPerson) = #_;
my $sqlPerson = "SELECT username, firstname FROM person WHERE sponsor_id = ?";
my $sthPerson = $dbhPerson->prepare($sqlPerson);
$sthPerson->execute($row['1']) or die "execution failed: $dbhPerson->errstr()";
while ( my #rowPerson = $sthPerson->fetchrow_array()){
print "<p>$rowPerson['0']</p>\n";
}
$sth->finish();
}
print "</td>\n";
print "<td>$row['0']</td>\n";
print "</tr>\n";
}
$sth->finish();
print "</tbody>\n";
print "</table>\n";
}
$dbh->disconnect();
However, I can't get the output what I am trying to achieve. Here is the result
content1
content2
content3
.....
relatedcontent1
It will just print one related content outside contents. Every content and its own at least 3 relatedcontent each.

Answer 1

You define your subroutines in the middle of other code in your program. This makes me think you expect them to be executed as they are defined, but that's not the case - they are executed as you call them. And you call them like this:
query_sponsor($dbh);
query_person_by_target($dbh);
So it should come as no surprise that you get all of the output from query_sponsor() followed by all of the output from query_person_by_name().
A far better approach would be to call query_person_by_target() from within query_sponsor(). I'd also split this into two phases - phase one to extract the data into a data structure and phase two to display that data.
As I don't have your database, this code is untested.
#!/usr/bin/perl
use strict;
use warnings;
use feature 'state'; # for state variables
use feature 'say';
use CGI 'header';
sub get_dbh {
# MySQL database configurations
my $dsn = "DBI:mysql:naxum";
my $username = "root";
my $password = '';
# connect to MySQL database
my %attr = (
PrintError=>0, # turn off error reporting via warn()
RaiseError=>1, # report error via die()
);
return DBI->connect($dsn, $username, $password, \%attr);
}
sub query_sponsor {
state $dbh = get_dbh();
my $sql = 'select name, id from sponsor';
my $sth = $dbh->prepare($sql);
$sth->execute;
my #sponsors;
while (my #row = $dbh->fetchrow_array) {
push #sponsors, {
name => $row[0],
id => $row[1],
people => get_people_for_sponsor($row[1]),
};
}
return #sponsors;
}
sub get_people_for_sponsor {
my ($sponsor_id) = #_;
state $dbh = get_dbh;
my $sql = 'select username, firstname
from person
where sponsor_id = ?';
my $sth = $dbh->prepare;
$sth->execute($sponsor_id);
my #people;
while (my #row = $sth->fetchrow_array) {
push #people, {
username => $row[0],
firstname => $row[1],
};
}
return \#people;
}
my #sponsors = query_sponsor();
# Now you have all of your data in #sponsors. You simply need
# to walk that array and use the data to build the output you
# want. My example is plain text - it shouldn't be too hard to
# convert it to HTML.
print header('text/plain');
for my $s (#sponsors) {
say "$s->{id}: $s->{name}";
for my $p (#{$s->{people}}) {
say "* $p->{firstname} / $p->{username}";
}
}
I'd also recommend that you look at using something like the Template Toolkit to produce your output. Putting raw HTML into your Perl program is a terrible idea - it is guaranteed to turn into an unmaintainable mess :-)

Answer 2

You have declared the two subroutines and you are calling one after one so it is executing like that for example consider the following one
sub1();
sub2();
sub sub1()
{
for(0..5)
{
print "hello\n";
sub sub2()
{
print "hi\n";
}
}
}
#output
hello
hello
hello
hello
hello
hello
hi
So you should remove the child query_person_by_target subroutine or call the child subroutine inside the parent subroutine query_sponsor and declare the child subroutine outside of the sub and loop, like below (not tested)
query_sponsor($dbh);
sub query_sponsor
{
# query from the table
my ($dbh) = #_;
my $sql = "SELECT name,id FROM sponsor";
my $sth = $dbh->prepare($sql);
# execute the query
$sth->execute();
print "<table>\n";
print "<thead>\n";
print "<tr>\n";
print "<th>Id</th>\n";
print "<th>Name</th>\n";
print "</tr>\n";
print "</thead>\n";
print "<tbody>\n";
while(my #row = $sth->fetchrow_array())
{
print "<tr>\n";
print "<td>\n";
print $row['1'];
query_person_by_target($dbh);
print "</td>\n";
print "<td>$row['0']</td>\n";
print "</tr>\n";
}
$sth->finish();
print "</tbody>\n";
print "</table>\n";
}
sub query_person_by_target{
my ($dbhPerson) = #_;
my $sqlPerson = "SELECT username, firstname FROM person WHERE sponsor_id = ?";
my $sthPerson = $dbhPerson->prepare($sqlPerson);
$sthPerson->execute($row['1']) or die "execution failed: $dbhPerson->errstr()";
while ( my #rowPerson = $sthPerson->fetchrow_array()){
print "<p>$rowPerson['0']</p>\n";
}
$sth->finish();
}
$dbh->disconnect();