有关数据库SQL递归查询在不同数据库中的实现方

//上查
with tmpTree
as
(
  select * from Tree where Id=2
  union all
  select p.* from tmpTree inner join Tree p on p.Id=tmpTree.ParentId
)
select * from tmpTree
 
//下查
with tmpTree
as
(
  select * from Tree where Id=2
  union all
  select s.* from tmpTree inner join Tree s on s.ParentId=tmpTree.Id
)
select * from tmpTree

SELECT *,TId.GetLevel() as [level] FROM Tree2 --获取所有层级
DECLARE @ParentTree hierarchyid
SELECT @ParentTree=TId FROM Tree2 WHERE Id=2
SELECT *,TId.GetLevel()AS [level] FROM Tree2 WHERE TId.IsDescendantOf(@ParentTree)=1 --获取指定的节点所有下级
DECLARE @ChildTree hierarchyid
SELECT @ChildTree=TId FROM Tree2 WHERE Id=3
SELECT *,TId.GetLevel()AS [level] FROM Tree2 WHERE @ChildTree.IsDescendantOf(TId)=1 --获取指定的节点所有上级

SELECT *
FROM Tree
START WITH Id=2
CONNECT BY PRIOR ID=ParentId --下查
SELECT *
FROM Tree
START WITH Id=2
CONNECT BY ID= PRIOR ParentId --上查

//定义一个依据ID查询所有父ID为这个指定的ID的字符串列表，以逗号分隔
CREATE DEFINER=`root`@`localhost` FUNCTION `getChildLst`(rootId int,direction int) RETURNS varchar(1000) CHARSET utf8
BEGIN
 DECLARE sTemp VARCHAR(5000);
  DECLARE sTempChd VARCHAR(1000);
  SET sTemp = '$';
  IF direction=1 THEN
   SET sTempChd =cast(rootId as CHAR);
  ELSEIF direction=2 THEN
   SELECT cast(ParentId as CHAR) into sTempChd FROM Tree WHERE Id=rootId;
  END IF;
  WHILE sTempChd is not null DO
    SET sTemp = concat(sTemp,',',sTempChd);
    SELECT group_concat(id) INTO sTempChd FROM Tree where (direction=1 and FIND_IN_SET(ParentId,sTempChd)>0)
    or (direction=2 and FIND_IN_SET(Id,sTempChd)>0);
  END WHILE;
RETURN sTemp;
END
//查询方法：
select * from tree where find_in_set(id,getChildLst(1,1));--下查
select * from tree where find_in_set(id,getChildLst(1,2));--上查

CREATE DEFINER=`root`@`localhost` FUNCTION `getChildLst`(rootId int,direction int) RETURNS varchar(1000) CHARSET utf8
BEGIN
 DECLARE sTemp VARCHAR(5000);
  DECLARE sTempChd VARCHAR(1000);
  SET sTemp = '$';
  SET sTempChd =cast(rootId as CHAR);
  
  IF direction=1 THEN
  WHILE sTempChd is not null DO
    SET sTemp = concat(sTemp,',',sTempChd);
    SELECT group_concat(id) INTO sTempChd FROM Tree where FIND_IN_SET(ParentId,sTempChd)>0;
  END WHILE;
  ELSEIF direction=2 THEN
  WHILE sTempChd is not null DO
    SET sTemp = concat(sTemp,',',sTempChd);
    SELECT group_concat(ParentId) INTO sTempChd FROM Tree where FIND_IN_SET(Id,sTempChd)>0;
  END WHILE;
  END IF;
RETURN sTemp;
END