sql 树查询 Oracle+Mysql

mysql:

根节点到子孙节点：（参考：https://www.2cto.com/database/201403/283731.html）

drop FUNCTION if EXISTS getChildList;
CREATE FUNCTION `getChildList`(rootId INT)
    RETURNS varchar(1000)
    BEGIN
      DECLARE sChildList VARCHAR(1000);
      DECLARE sChildTemp VARCHAR(1000);
      SET sChildTemp =cast(rootId as CHAR);
      WHILE sChildTemp is not null DO
        IF (sChildList is not null) THEN
          SET sChildList = concat(sChildList,',',sChildTemp);
    ELSE
      SET sChildList = concat(sChildTemp);
    END IF;
        SELECT group_concat(id) INTO sChildTemp FROM user_role where FIND_IN_SET(parentid,sChildTemp)>0;
      END WHILE;
      RETURN sChildList;
    END;
/*获取子节点*/
/*调用: 1、select getChildList(0) id; 2、select * 5From user_role where FIND_IN_SET(id, getChildList(2));*/
 
 

子节点到根节点

drop FUNCTION if EXISTS getParentList;
CREATE FUNCTION `getParentList`(rootId INT)
    RETURNS varchar(1000)
    BEGIN
      DECLARE sParentList varchar(1000);
      DECLARE sParentTemp varchar(1000);
      SET sParentTemp =cast(rootId as CHAR);
      WHILE sParentTemp is not null DO
    IF (sParentList is not null) THEN
         SET sParentList = concat(sParentTemp,',',sParentList);
    ELSE
     SET sParentList = concat(sParentTemp);
    END IF;
        SELECT group_concat(parentid) INTO sParentTemp FROM user_role where FIND_IN_SET(id,sParentTemp)>0;
      END WHILE;
      RETURN sParentList;
    END;
/*获取父节点*/
/*调用: 1、select getParentList(6) id; 2、select * From user_role where FIND_IN_SET(id, getParentList(2));*/

oracle:

子节点向根节 level 关键字指所在层次

select level,a.* from TF_REGION a start with REGION_CODE =130000  connect by prior PARENT_CODE =REGION_CODE

START WITH...CONNECT BY PRIOR子句实现递归查询

--根据regioncode 获取国家code (获取最高级)
select    distinct(REGION_CODE)  from (
              SELECT * FROM TF_REGION g START WITH g.REGION_CODE =5002 
                    CONNECT BY PRIOR 
                        g.PARENT_CODE = g.REGION_CODE
                            ) t  where nvl(t.DEL_FLAG,0)=0  and t.region_level=1 ;
 

根节点遍历子节点

select level,a.* from TF_REGION a start with PARENT_CODE=1 connect by prior  REGION_CODE=PARENT_CODE

注意：最后的REGION_CODE=PARENT_CODE 是包括子孙节点，PARENT_CODE=REGION_CODE是只有子节点

start with 后面所跟的就是就是递归的种子，也就是递归开始的地方；

connect by  prior后面的字段顺序是有讲究的；