public function exists($query, string $separator = 'AND', bool $not = false)
	{
		if($query instanceof Closure)
		{
			$query = new Subquery($query);
		}

		$this->wheres[] =
		[
			'type'      => 'exists',
			'query'     => $query,
			'separator' => $separator,
			'not'       => $not,
		];

		return $this;
	}