Clarification cascade_* attribute defaults documentation

[dbsrgits/DBIx-Class-Historic.git] / lib / DBIx / Class / Manual / Glossary.pod

=head1 NAME

DBIx::Class::Manual::Glossary - Clarification of terms used.

=head1 INTRODUCTION

This document lists various terms used in DBIx::Class and attempts to
explain them.

=head1 TERMS

=head2 DB schema

Refers to a single physical schema within an RDBMS. Synonymous with the terms
'database', for MySQL; and 'schema', for most other RDBMS(s).

In other words, it's the 'xyz' _thing_ you're connecting to when using any of
the following L<DSN|DBI/connect>(s):

  dbi:DriverName:xyz@hostname:port
  dbi:DriverName:database=xyz;host=hostname;port=port

=head2 Inflation

The act of turning database row data into objects in
language-space. DBIx::Class further allows you to inflate your data
into perl objects which more usefully represent their contents. For
example: L<DBIx::Class::InflateColumn::DateTime> for datetime or
timestamp column data.

=head2 Join

This is an SQL keyword that gets mentioned a lot. It is used to fetch
data from more than one table at once, by C<join>ing the tables on
fields where they have common data.

=head2 Normalisation

A normalised database is a sane database. Each table contains only
data belonging to one concept, related tables refer to the key field
or fields of each other. Some links to webpages about normalisation
can be found in L<DBIx::Class::Manual::FAQ|the FAQ>.

=head2 ORM

Object-relational mapping, or Object-relationship modelling. Either
way it's a method of mapping the contents of database tables (rows),
to objects in programming-language-space. DBIx::Class is an ORM.

=head2 Relationship

In DBIx::Class a relationship defines the connection between exactly
two tables. The relationship condition lists the columns in each table
that contain the same values. It is used to output an SQL JOIN
condition between the tables.

=head2 Relationship bridge

A relationship bridge, such as C<many_to_many> defines an accessor to
retrieve row contents across multiple relationships.

=head2 ResultSet

This is an object representing a set of data. It can either be an
entire table, or the results of a query. The actual data is not held
in the ResultSet, it is only a description of how to fetch the data.

See also: L<DBIx::Class::ResultSet/METHODS>

=head2 ResultSource

ResultSource objects represent the source of your data, they are also known as
a table objects. 

See also: L<DBIx::Class::ResultSource/METHODS>

=head2 Record

See Row.

=head2 Row

Row objects contain your actual data. They are returned from ResultSet objects.

=head2 Object

See Row.

=head2 Schema

A Schema object represents your entire table collection, plus the
connection to the database. You can create one or more schema objects,
connected to various databases, with various users, using the same set
of table (ResultSource) definitions.