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Re^4: Relational table with perl DBI

by Neighbour (Friar)
on Mar 13, 2013 at 12:30 UTC ( #1023184=note: print w/replies, xml ) Need Help??

in reply to Re^3: Relational table with perl DBI
in thread Relational table with perl DBI

First off, very nice how you improved on the insert query, for example when building the $field_placeholders.

In order to get the relations properly, you'll learn about another nifty feature of perl: hashes. A hash is an unsorted list of key-value pairs.
We're going to loop through the files, accumulating the data per file in $hr_output and accumulating all per-file data in $ar_data.
The prefixes hr_ and ar_ are not required by perl, but they help me to distinguish between references to hashes (hashref, or hr) and references to arrays (arrayref, or ar).
my $ar_data = []; #Opening, reading, and extracting column content of each concord.n.txt + file foreach my $output_concord_file (@output_concord_files){ #Note : for the concord file, no processing implied -> stored by d +efault in $output_concord_file open (my $fh, '<:utf8', "$output_concord_file") || die "Couldn't o +pen $output_concord_file : $!"; my $hr_output = {}; $hr_output->{concord_file} = $output_concord_file; while (<$fh>){ if ($_ =~ /=\[=(.*)=\]=/){ $hr_output->{url} = $1; } if ($_ =~ /=\[\+(.*)\+\]=/){ $hr_output->{sys_time} = $1; } if ($_ =~ /=E-(.*)=event/){ push(@{$hr_output->{events}}, $1); } } push(@{$ar_data}, $hr_output); close ($fh); }
I'm not quite sure what you intended to do to those html-pages, and i'm not sure that what's happening is what you really want, so I'm just going to skip that :P
Next up is inserting all accumulated data:
if (@{$ar_data}) { # If there is any data, prepare the query my @fields = keys %{$ar_data->[0]}; # Extract all the keys from th +e first element of ar_data my $fieldlist = join(',', @fields); my $field_placeholders = join(',', map {'?'} @fields); my $sth_insert_article = $dbh->prepare( qq( INSERT INTO article ($fieldlist) VALUES ($field_placeholders) )); my $sth_select_last_insert_id = $dbh->prepare( qq( SELECT LAST_INS +ERT_ID )); my $sth_insert_event = $dbh->prepare( qq( INSERT INTO event (event) VALUES (?) )); my $sth_insert_article_event = $dbh->prepare( qq( INSERT INTO article_event_index (id_article, id_event) VALUES +(?,?) )); # Now we loop over and insert all data foreach my $hr_output (@{$ar_data}) { # Insert article data my $inserted_records = $sth_insert_article->execute(@{$hr_outp +ut}{@fields}); # Ok, I admit, this one is really tricky to read :) if ($inserted_records != 1) { die "Error inserting article [$h +r_output->{url}], only [$inserted_records] got inserted: " . $sth_ins +ert_article->errstr; } # Get article ID my $article_id = ($dbh->selectcol_arrayref($sth_select_last_in +sert_id))->[0]; # Insert events foreach my $event (@{$hr_output->{events}}) { $inserted_records = $sth_insert_event->execute($event); if ($inserted_records != 1) { die "Error inserting event [ +$event], only [$inserted_records] got inserted: " . $sth_insert_event +->errstr; } # Get event ID my $event_id = ($dbh->selectcol_arrayref($sth_select_last_ +insert_id))->[0]; # Insert article_event combo $inserted_records = $sth_insert_article_event->execute($ar +ticle_id, $event_id); if ($inserted_records != 1) { die "Error inserting article +-event [$article_id, $event_id], only [$inserted_records] got inserte +d: " . $sth_insert_article_event->errstr; } } } }
This follows the loop I described in my previous post. There are a few tricks here, which I'll leave for you to figure out (you can still ask though :)).
The most unreadable trick is @{$hr_output}{@fields} which produces an array of the value-parts of the hashref for all @fields, in order of those @fields.

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Re^5: Relational table with perl DBI
by M15U (Acolyte) on Mar 13, 2013 at 13:55 UTC

    Thank you very much for your answer. I though that at some point I'll have to use hashes, but I was always afraid of them. I understand your code and I tried to incorporate it in my own. I've already seen on the web the @{$hr_output}{@fields} syntax, though in this context it's the only time when I get it.

    However I have a small program in the code. I get :

    "DBD::mysql::st execute failed: Unknown column 'event' in 'field list' at line 289. DBD::mysql::db selectcol_arrayref failed: Unknown column 'LAST_INSERT_ID' in 'field list' at line 292. Can't use an undefined value as an ARRAY reference at line 292. "

    I don't really see where do the script bug.

    And also the first "if" error managment loop gives me :

    "Use of uninitialized value $inserted_records in numeric ne (!=) at line 290. Use of uninitialized value $inserted_records in concatenation (.) or string at line 290. Error inserting article, only [] got inserted: Unknown column 'event' in 'field list' at line 290."

    Though thank you very much again.

      I think I know where the problem is. When I print "@fields" if get : concord_file sys_time url event

      The thing is I have two tables:

      article : id_article url html_extr concord_file sys_time

      event : id_event event

      I don't really know how to reorder this two fields

        Now I really got it. Using the placeholders method for filling the tables requires the precise order of the column. Using a hash means that all data is scrambled

        Plus, in this aproach the 'event' column is in the same table as the article.

        Is there a away to reorder a hash index following a specific pattern ? how can I get the 'event' column to be treate separetly of the article table ?

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