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DBIx-Table2Hash-1.00
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/ DBIx::Table2Hash

NAME

DBIx::Table2Hash - Read a database table into a hash

Version

This document refers to version 1.00 of DBIx::Table2Hash, released 8-Jan-2003.

Synopsis

#!/usr/bin/perl

my($hash_ref) = DBIx::Table2Hash -> new
(
	dbh          => $dbh,
	table_name   => $table_name,
	key_column   => 'name',
	value_column => 'id'
) -> select();

Description

DBIx::Table2Hash is a pure Perl module.

This module reads a database table and stores keys and values in a hash. The resultant hash is not nested in any way.

The aim is to create a hash which is a simple look-up table. To this end, the module allows the key_column to point to an SQL expression.

Constructor and initialization

new(...) returns a DBIx::Table2Hash object.

This is the class's contructor.

Parameters:

  • dbh

    A database handle.

  • table_name

    The name of the table to select from.

  • key_column

    The name of the column, or SQL expression, to use for hash keys.

    Say you have 2 columns, called col_a and col_b. Then you can concatenate them with:

    key_column => 'concat(col_a, col_b)'

    or, even fancier,

    key_column => "concat(col_a, '-', col_b)"

  • value_column

    The name of the column to use for hash values.

  • where

    The optional where clause, including the word 'where', to add to the select.

Method: new(...)

Returns a object of type DBIx::Table2Hash.

See above, in the section called 'Constructor and initialization'.

Method: select()

Returns a hash ref.

Calling select() actually executes the SQL select statement, and builds the hash.

Required Modules

DBI, so you can provide a database handle.

Changes

See Changes.txt.

FAQ

Q: What is the point of this module?

A: To be able to restore a hash from a database rather than from a file.

Q: Can your other module DBIx::Hash2Table be used to save the hash back to the database?

A: Sure.

Q: Are there any other modules with similar capabilities?

A: Yes:

  • DBIx::Lookup::Field

    Quite similar.

  • DBIx::TableHash

    This module takes a very long set of parameters, but unfortunately does not take a database handle.

    It does mean the module, being extremely complex, can read in more than one column as the value of a hash key, and it has caching abilities too.

    It works by tieing a hash to an MySQL table, and hence supports writing to the table. It uses MySQL-specific code, for example, when it locks tables.

    Unfortunately, it does not use data binding, so it cannot handle data which contains single quotes!

    Further, it uses /^\w+$/ to 'validate' column names, so it cannot accept an SQL expression instead of a column name.

    Lastly, it also uses /^\w+$/ to 'validate' table names, so it cannot accept table names and views containing spaces and other 'funny' characters, eg '&' (both of which I have to deal with under MS Access).

  • DBIx::Tree

    This module is more like the inverse of DBIx::Hash2Table, in that it assumes you are building a nested hash.

    As it reads the database table it calls a call-back sub, which you use to process the rows of the table.

Author

DBIx::Table2Hash was written by Ron Savage <ron@savage.net.au> in 2003.

Home page: http://savage.net.au/index.html

Copyright

Australian copyright (c) 2003, Ron Savage. All rights reserved.

All Programs of mine are 'OSI Certified Open Source Software';
you can redistribute them and/or modify them under the terms of
The Artistic License, a copy of which is available at:
http://www.opensource.org/licenses/index.html