/** * Creates an instance of binary expression node, representing the construction: subject NOT NOT NULL * * @param mixed $subject logical subject * * SQL example: * @code * // "id" IS NOT NULL * Expression::notNull("id"); * @endcode * @return UnaryPostfixExpression */ static function notNull($subject) { return new UnaryPostfixExpression($subject, UnaryPostfixLogicalOperator::isNotNull()); }