在MYSQL中如何统计树形结构的业务数量及其更新策略？

--  计算指定节点及其子节点的总人口数量
DELIMITER //
CREATE PROCEDURE CalculateTotalPopulation(IN nodeId INT, OUT totalPopulation INT)
BEGIN
  DECLARE finished INTEGER DEFAULT 0;
  DECLARE childId INT;
  DECLARE populationCursor CURSOR FOR SELECT id FROM your_table WHERE parentId = nodeId;
  DECLARE CONTINUE HANDLER FOR NOT FOUND SET finished = 1;

  SET totalPopulation = (SELECT num FROM your_table WHERE id = nodeId);

  OPEN populationCursor;
  read_loop: LOOP
    FETCH populationCursor INTO childId;
    IF finished = 1 THEN
      LEAVE read_loop;
    END IF;
    CALL CalculateTotalPopulation(childId, @childPopulation);
    SET totalPopulation = totalPopulation + @childPopulation;
  END LOOP;
  CLOSE populationCursor;
END //
DELIMITER ;

DELIMITER //
CREATE TRIGGER update_parent_population
AFTER UPDATE ON your_table
FOR EACH ROW
BEGIN
  IF NEW.type = 3 THEN
    CALL UpdateParentPopulation(NEW.id);
  END IF;
END //
DELIMITER ;

-- 更新父节点人口数量的存储过程 (需根据实际表结构修改)
DELIMITER //
CREATE PROCEDURE UpdateParentPopulation(IN nodeId INT)
BEGIN
  DECLARE parentId INT;
  SET parentId = (SELECT parentId FROM your_table WHERE id = nodeId);
  WHILE parentId IS NOT NULL DO
    UPDATE your_table SET num = (SELECT SUM(num) FROM your_table WHERE parentId = parentId) WHERE id = parentId;
    SET parentId = (SELECT parentId FROM your_table WHERE id = parentId);
  END WHILE;
END //
DELIMITER ;