NAME

Class::ReluctantORM::SQL::Expression::Criterion - Represent WHERE and JOIN criteria

SYNOPSIS

  # Save yourself some typing
  use Class::ReluctantORM::SQL::Aliases;

  # This creates an "always true" criteria
  my $crit = Criterion->new_tautology();

  # This creates '1=1'
  my $crit1 = Criterion->new('=', 1, 1);

  # This creates 'my_column = ?'
  my $crit2 = Criterion->new(
                             '=',
                             Column->new(column =>'my_column',
                             Param->new(),
                            );

  # Wrap $crit2 in NOT ( 'NOT my_column = ?' )
  my $crit3 = Criterion->new('NOT', $crit2);

  # Make '(1=1) AND (NOT (my_column = ?))'
  my $crit4 = Criterion->new('AND', $crit1, $crit3);

  # Make a where clause with this as its root
  my $where = Where->new($crit4);

  # Or AND it to an existing one
  $where2->and($crit4);

  # Dump a Criterion as a string (for diagnostics only - NOT RBMS safe)
  my $str = $crit->pretty_print();  # Verbose
  my $str = $crit->pretty_print(one_line => 1);

DESCRIPTION

Represents a boolean-return predicate call, as needed in JOIN criteria and WHERE clauses.

This is a specialized subclass of a FunctionCall.

CONSTRUCTORS

$crit = SQL::Expression::Criterion->new();

$crit = SQL::Expression::Criterion->new($op_name, $exp1, [$exp2, ...]);

$crit = SQL::Expression::Criterion->new($function, $exp1, [$exp2, ...]);

Creates a new criterion.

In the first form, returns an always true criterion.

In the second and third form, creates a new criterion using the specified operator and argument(s). An exception will be thrown if the number of arguments does not match the operator's arity.

$op is a string name of a Function. Case is ignored.

$expN is either a Class::ReluctantORM::SQL::Expression subclass, or a plain scalar, or undef. Scalars and undefs will be "autoboxed" into being Class::ReluctantORM::SQL::Expression::Literal objects, with undefs becoming NULLs.

$crit = SQL::Expression::Criterion->new_tautology();

Returns an 'always true' criterion.

ACCESSORS

@args = $crit->arguments();

Returns the arguments of the criterion.

@args = $crit->child_expressions();

Returns the child nodes of this node (same as arguments()). Required by the Expression interface.

$bool = $arg->is_criterion();

All objects of this class return true. The class adds this method to Expression, making all other subclasses of it return false.

$bool = $crit->is_leaf_expression();

Always returns false for this class. Required by the Expression interface.

$func = $crit->function();

Returns the Function that represents the operator.

$str = $crit->pretty_print();

Renders a human-readable representation of the Criterion.

$bool = $crit->is_equivalent($other_crit);

Returns true if the two criteria are certainly equivalent (does not check table or column aliases).

Returns false otherwise.

AUTHOR

Clinton Wolfe January 2009, January 2010

cpanm Class::ReluctantORM

perl -MCPAN -e shell
install Class::ReluctantORM