Name
    SQL

Description
    This module serves as a framework for object persistence via a SQL
    database. Interaction with an underlying database is accomplished via
    Perl objects that abstract away all of the tedious construction,
    issuance, and processing of SQL queries. Within this framework, users
    may create, modify and delete objects, as well as link them together in
    arbitrary ways, and perform a variety of querying operations.

    Divided into several conceptual components, this module provides several
    well isolated sub-components that are reasonably easy to understand on
    their own. Short descriptions of these modules may be found in the
    following section.

Modules
    SQL::Object
        If any class were said to lie at the center of this module, this
        would be the one. This class serves as the base class for all object
        types, and provides a collection of methods for performing all
        common operations, such as saving, modifying, and deleting it.
        Sub-classes to this class must provide a get_table_name() method,
        and will probably also include various and sundry wrapper methods to
        flesh out the functionality of the class. One can load single
        objects via themselves, or obtain collections of objects by using
        the SQL::Object::Query class.

    SQL::Object::Query
        This class is used to specify a query of a collection of objects.
        Queries of this type are specified with conditions, bindings of
        condition variables to values, and orderings. One may additionally
        specify a list of SQL::Link::Query objects which will specify that
        the objects loaded should be loaded with certain parent and/or
        children objects. When the execute() method is invoked, a
        SQL::Object::ResultSet object is returned.

    SQL::Object::ResultSet
        A SQL::Object::ResultSet object is the result of executing a query
        specified by a SQL::Object::Query object. By repeatedly invoking the
        get_next_result() method until it returns undef, one can iterate
        over the results of a query, getting back instances of classes that
        derive from SQL::Object.

    SQL::Link
        A SQL::Link object specifies a linking relationship in the database,
        and also provides mechanisms for creating, modifying and deleting
        relationships between objects as specified by the link in question.

    SQL::Link::Query
        A SQL::Link::Query object is used to specify a query of a collection
        of linked objects. Queries of this type are specified with a
        SQL::Link object, conditions, bindings of condition variables to
        values, and orderings. When the execute() method is invoked, a
        SQL::Link::ResultSet object is returned.

    SQL::Link::ResultSet
        A SQL::Link::ResultSet object is the result of executing a query
        specified by a SQL::Link::Query object. By repeatedly invoking the
        get_next_result() method until it returns undef, one can iterate
        over the results of a query, getting back instances of the
        SQL::Link::Result class.

    SQL::Table
        A SQL::Table object contains all available information about a
        database table. It holds a collection of SQL::Column objects, and
        indexes them in useful ways. Users will probably never have need to
        create a SQL::Table object directly. Rather, the SQL::Object class
        provides a get_table() method that returns an object of this type.
        The table returned is contingent upon the derived class's
        get_table_name() method. Using the name of the table, SQL::Row
        constructs a SQL::Table object which populates itself with table
        structure information by querying the database.

    SQL::Column
        A SQL::Column object contains all of the attributes of a column of a
        database table. Such information includes name, type, and keying.

    SQL::Statement
        The SQL::Statement class is a base class for several derived
        classes, each of which provides for a certain type of SQL statement.
        This class takes table names, field names, conditions, orderings,
        and other such statement parameters, and then via the stringify()
        method returns a scalar that holds the statement string.

    SQL::Util
        This class holds a collection of static utility methods that allow
        for performing common database tasks.

    SQL::Conf
        The SQL::Conf class is a base class for classes that parse
        connection configuration information for various RDBMS, e.g.
        SQL::Conf::MySQL.

    SQL::DBH
        The SQL::DBH class has but a single static method, create_handle(),
        which creates database handles via calling DBI->connect(...).

Environment Variables
    SQLRDBMS
        This environment variable specifies the default value to be used by
        SQL::DBH in specifying the type of database to which a connection
        will be made. Presently the only supported value is 'MySQL'. This
        value allows SQL::DBH::create_handle() to figure out which derived
        class of SQL::Conf to instantiate, though one may instead pass an
        argument to it to specify the RDBMS explicitly.

    SQLCNXNCONF
        This environment variable specifies the default value to be used by
        SQL::DBH::create_handle() when using a SQL::Conf subclass to parse
        the configuration information for a database connection.