NAME¶

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

INTRODUCTION¶

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

DBIx::Class TERMS¶

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 DSN(s):

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

Inflation¶

The act of turning database row data into objects in language-space. DBIx::Class result classes can be set up to inflate your data into perl objects which more usefully represent their contents. For example: DBIx::Class::InflateColumn::DateTime for datetime or timestamp column data. See also DBIx::Class::InflateColumn.

Deflation¶

The opposite of "Inflation". Existing perl objects that represent column values can be passed to DBIx::Class methods to store into the database. For example a DateTime object can be automatically deflated into a datetime string for insertion. See DBIx::Class::InflateColumn and other modules in that namespace.

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.

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.

Relationship bridge¶

A relationship bridge, such as "many_to_many" defines an accessor to retrieve row contents across multiple relationships. The difference between a bridge and a relationship is, that the bridge cannot be used to "join" tables in a "search", instead its component relationships must be used.

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 "Result Class" definitions. At least one DBIx::Class::Schema class is needed per database.

Result Class¶

A Result class defines both a source of data (usually one per table), and the methods that will be available in the "Result" objects created using that source. One Result class is needed per data source (table, view, query) used in your application, they should inherit from DBIx::Class::Core. See also: DBIx::Class::Manual::ResultClass

ResultSource¶

ResultSource objects represent the source of your data, these are sometimes (incorrectly) called table objects. ResultSources do not need to be directly created, a ResultSource instance is created for each "Result Class" in your "Schema", by the proxied methods "table" and "add_columns". See also: "METHODS" in DBIx::Class::ResultSource

ResultSet¶

This is an object representing a set of conditions to filter 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: "METHODS" in DBIx::Class::ResultSet

Result¶

Result objects contain your actual data. They are returned from ResultSet objects. These are sometimes (incorrectly) called row objects, including older versions of the DBIC documentation. See also: DBIx::Class::Manual::ResultClass

Row¶

See Result.

Object¶

See Result.

Record¶

See Result.

prefetch¶

Similar to a join, except the related result objects are fetched and cached for future use, instead of used directly from the ResultSet. This allows you to jump to different relationships within a Result without worrying about generating a ton of extra SELECT statements.

SQL TERMS¶

CRUD¶

Create, Read, Update, Delete. A general concept of something that can do all four operations (INSERT, SELECT, UPDATE, DELETE), usually at a row-level.

Join¶

This is an SQL keyword, it is used to link multiple tables in one SQL statement. This enables us to fetch data from more than one table at once, or filter data based on content in another table, without having to issue multiple SQL queries.

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 the FAQ.

Related data¶

In SQL, related data actually refers to data that are normalised into the same table. (Yes. DBIC does mis-use this term.)

FURTHER QUESTIONS?¶

Check the list of additional DBIC resources.

COPYRIGHT AND LICENSE¶

This module is free software copyright by the DBIx::Class (DBIC) authors. You can redistribute it and/or modify it under the same terms as the DBIx::Class library.