protected function compileNestedJoinConstraint(array $clause)
	{
		$clauses = [];

		foreach ($clause['join']->clauses as $nestedClause) {
			$clauses[] = $this->compileJoinConstraint($nestedClause);
		}

		$clauses[0] = $this->removeLeadingBoolean($clauses[0]);

		$clauses = implode(' ', $clauses);

		return "{$clause['boolean']} ({$clauses})";
	}