NAME¶

Alzabo::Create::ForeignKey - Foreign key objects for schema creation.

SYNOPSIS¶

  use Alzabo::Create::ForeignKey;

DESCRIPTION¶

A foreign key is an object defined by several properties. It represents a relationship from a column or columns in one table to a column or columns in another table. This relationship is defined by its cardinality (one to one, one to many, or many to one) and its dependencies (whether or not table X is dependent on table Y, and vice versa). Many to many relationships are not allowed. However, you may indicate such a relationship when using the Alzabo::Create::Schema->add_relation method method, and it will create the necessary intermediate linking table for you.

INHERITS FROM¶

"Alzabo::ForeignKey" Note: all relevant documentation from the superclass has been merged into this document.

METHODS¶

new The constructor takes the following parameters:

* columns_from => "Alzabo::Create::Column" object(s)

* columns_to => "Alzabo::Create::Column" object(s)

These two parameters may be either a single column or a reference to an array columns. The number of columns in the two parameters must match.

* cardinality => [1, 1], [1, 'n'], or ['n', 1]

* from_is_dependent => $boolean

* to_is_dependent => $boolean

* comment => $comment

An optional comment.

It returns a new "Alzabo::Create::ForeignKey" object. Throws: "Alzabo::Exception::Params" table_from table_to Returns the relevant "Alzabo::Create::Table" object. columns_from columns_to Returns the relevant "Alzabo::Create::Column" object(s) for the property as an array. column_pairs Returns an array of array references. The references are to two column array of "Alzabo::Create::Column" objects. These two columns correspond in the tables being linked together. set_columns_from ("Alzabo::Create::Column" object(s)) Sets the column(s) that the relation is from. This can be either a single column object or a reference to an array of column objects. Throws: "Alzabo::Exception::Params" set_columns_to ("Alzabo::Create::Column" object(s)) Sets the column(s) that the relation is to. This can be either a single column object or a reference to an array of column objects. Throws: "Alzabo::Exception::Params" cardinality Returns a two element array containing the two portions of the cardinality of the relationship. Each portion will be either '1' or 'n'. from_is_dependent to_is_dependent Returns a boolean value indicating whether there is a dependency from one table to the other. is_one_to_one is_one_to_many is_many_to_one Returns a boolean value indicating what kind of relationship the object represents. set_cardinality (\@cardinality) see above for details Sets the cardinality of the foreign key. Throws: "Alzabo::Exception::Params" set_from_is_dependent ($boolean) Indicates whether or not the first table in the foreign key is dependent on the other (i.e. whether the 'from' table is dependent on the 'to' table). set_to_is_dependent ($boolean) Indicates whether or not the second table in the foreign key is dependent on the other (i.e. whether the 'to' table is dependent on the 'from' table). id Returns a string uniquely identifying the foreign key. is_same_relationship_as ($fk) Given a foreign key object, this returns true if the two objects represent the same relationship. However, the two objects may represent the same relationship from different table's points of view. comment Returns the comment associated with the foreign key object, if any. set_comment ($comment) Sets the comment for the foreign key object.

AUTHOR¶

Dave Rolsky, <autarch@urth.org>