NAME

Class::ReluctantORM::SQL::SubQuery - Represent a sub-SELECT in a FROM or WHERE clause

SYNOPSIS

  use Class::ReluctantORM::SQL::Aliases;

  # Make a SELECT as usual
  my $select = SQL->new('select');
  $select->from(Table->new(table => 'mytable');
  $select->where(Criterion->new('=', 1,1));

  # Make a subquery
  my $subquery = SubQuery->new($select);

  # Use it as an expression
  my $in_crit = Criterion->new(
                               'IN',
                               'needle',
                               $subquery, # haystack
                              );


  # Or use it as a JOIN relation
  # TODO DOCS

DESCRIPTION

Wrapper around a SELECT statement, that implements both the Expression interface as well as the Relation interface, allowing it to be used in a WHERE clause or FROM clause.

CONSTRUCTOR

$sq = SubQuery->new($select);

Creates a new SubQuery containing the SQL object given by $select. The SQL object's operation must be 'SELECT'.

ACCESSORS

$sql = $sq->statement();

$sq->statement($sql);

Sets or reads the underlying SQL object.

$bool = $sq->is_subquery();

All objects of this class return true. The class adds this method to both Expression and Relation, making all other subclasses of them return false.

$sq->alias('my_alias');

$alias = $sq->alias();

From Relation interface.

Reads or sets the alias used for this relation in FROM clauses.

$str = $sq->pretty_print();

From both Expression and Relation interfaces.

Renders a human-readable version of the relation to a string.

@cols = $sq->columns()

Returns a list of re-aliased columns returned by the subquery. This presents the externally visible set of columns.

From Relation interface.

$bool = $sq->has_column('col_name')

Returns a boolean indicating whether a column is present in the external columns returned. The name will be the re-aliased name.

From Relation interface.

$bool = $sq->knows_all_columns()

Returns a boolean indicating whether all output columns are known in advance from this relation. Always returns true for SubQueries.

From Relation interface.

$bool = $sq->knows_any_columns()

Returns a boolean indicating whether any output columns are known in advance from this relation. Always returns true.

From Relation interface.

@tables = $sq->tables(%opts);

Returns a list of all tables referenced in the FROM clause of the subquery.

From the Relation interface.

If the exclude_subqueries option is enabled, this returns an empty list.

@rels = $sq->child_relations();

Always returns an empty list. If you want to access the relations in the subquery, use $sq->statement->from->child_relations().

From the Relation interface.

$bool = $sq->is_leaf_relation();

Indicates if the object is a terminal point on the From tree. Always returns true.

From the Relation interface.

$rel = $sq->parent_relation();

Returns the parent node of the object. If undefined, this is the root node.

From the Relation interface.

$bool = $sq->is_leaf_expression();

Indicates if the object is a terminal point on the Expression tree. Always returns true.

@exps = $sq->child_expressions();

Always returns an empty list.

$exp = $sq->parent_expression();

Returns the parent node of the expression. If undefined, this is the root node.

$clone = $sq->clone()

Creates a new SubQuery whose statement is a clone of the original's statement.

AUTHOR

Clinton Wolfe January 2010

cpanm Class::ReluctantORM

perl -MCPAN -e shell
install Class::ReluctantORM