NAME

Persist::Join - Data abstraction representing the joining of multiple tables

SYNOPSIS

  use Persist::Source;

  # For joins where a FOREIGN KEY may be used to perform the join implicitly
  $source = new Persist::Source(...);
  $join = $source->join([ 'Folks', 'Favorites' ], 
                        [ undef, "color = 'Blue'" ]);

  print "Folks with whose favorite color is Blue:\n";
  while ($join->next) {
	  print $join->name, "\n";
  }

  # For explicit joins where there is no foreign key, to join a table to itself,
  # tables have multiple foreign keys between each otheror implicit joining is
  # undesirable
  $join = $source->join(-tables => [ 'Folks', 'Favorites' ],
                        -on     => [ "1.fid = 2.fid" ],
                        -filter => "Favorites.color = 'Blue'");

DESCRIPTION

This abstraction allows for easy access to multiple joined tables. It is an extension of Persist::Tabular and most of the functionality available is documented there.

$join = $source->join($tables [, $on, $filters, \@order, $offset, $limit ])

See Persist::Source for details.

$row = $join->table($table)

When first or next have been passed the $bytable option set to true, you must use this method to retrieve data from each table. Essentially, the current row is packed with data from multiple tables instead of retrieving the joined information as if it were combined into a single table.

The $table argument may be any valid table identifier that could be used in a table. That is, given a join on tables ['A', 'B', 'A'], you could pass a value of 1 to retrieve data for the first "A" table, 2 to retrieve data for the "B" table, or 3 to retrieve data for the second "A" table. You could pass "B" to retrieve data for the "B" table. Finally, you could pass "A1", "B1", and "A2" to access each of these tables, respectively. Using an a name that is ambiguous (like "A" in this example) will result in an error.

$tabular-><table>

Shortcut for of table that returns the data found in the given table. This is only available when the $bytable option was passed to the last call to first or next. Otherwise, it is assumed that this is a column name rather than a table.

See <column>.

SEE ALSO

Persist::Tabular, Persist::Source

AUTHOR

Andrew Sterling Hanenkamp, <hanenkamp@users.sourceforge.net>

COPYRIGHT AND LICENSE

Copyright (c) 2003, Andrew Sterling Hanenkamp
All rights reserved.

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