Re: DBI relation between tables tutorial

[daxim]

This is a beginner database question, go to the next library and get an introduction to RDBMS design/SQL book.

You are describing a Junction table.

$ echo '
    create table articles (id integer not null, parsed text, primary k
+ey (id));
    create table information (id integer not null, something text, pri
+mary key (id));
    create table articles_information (articles_id integer not null, i
+nformation_id integer not null, primary key (articles_id, information
+_id), foreign key (articles_id) references articles (id), foreign key
+ (information_id) references information (id));
' | sqlite3 M15U.sqlite

This example is already complicated enough that you should not bother with raw SQL in DBI, but use a higher-level ORM. DBIx::Class sample code:

use DBIx::Class::Schema::Loader qw();
DBIx::Class::Schema::Loader->naming('preserve');
my $schema = DBIx::Class::Schema::Loader->connect('DBI:SQLite:db=M15U.
+sqlite');
my $foobar = $schema->resultset('Articles')->create({ id => 1, parsed 
+=> 'foo bar' });
$foobar->add_to_informations({ id => 1, something => 'quux' });
$foobar->add_to_informations({ id => 2, something => 'fnord' });

As long as the foreign keys are set up properly, the junction table is filled automatically:

$ echo .dump | sqlite3 M15U.sqlite | grep INSERT
INSERT INTO "articles" VALUES(1,'foo bar');
INSERT INTO "information" VALUES(1,'quux');
INSERT INTO "information" VALUES(2,'fnord');
INSERT INTO "articles_information" VALUES(1,1);
INSERT INTO "articles_information" VALUES(1,2);