MySQL查询树结构方式

CREATE TABLE `tree`  (
  `id` bigint(11) NOT NULL,
  `pid` bigint(11) NULL DEFAULT NULL,
  `name` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;
INSERT INTO `tree` VALUES (1, 0, '中国');
INSERT INTO `tree` VALUES (2, 1, '四川省');
INSERT INTO `tree` VALUES (3, 2, '成都市');
INSERT INTO `tree` VALUES (4, 3, '武侯区');
INSERT INTO `tree` VALUES (5, 4, '红牌楼');
INSERT INTO `tree` VALUES (6, 1, '广东省');
INSERT INTO `tree` VALUES (7, 1, '浙江省');
INSERT INTO `tree` VALUES (8, 6, '广州市');

CREATE FUNCTioN `GET_CHILD_node`(rootId varchar(100))   
RETURNS varchar(2000)  
BEGIN   
DECLARE str varchar(2000);  
DECLARE cid varchar(100);   
SET str = '$';   
SET cid = rootId;   
WHILE cid is not null DO   
    SET str = concat(str, ',', cid);   
    SELECT group_concat(id) INTO cid FROM tree where FIND_IN_SET(pid, cid);   
END WHILE;   
RETURN str;   
END

select * from tree where FIND_IN_SET(id, GET_CHILD_NODE(2));

CREATE FUNCTION `GET_PARENT_NODE`(rootId varchar(100))   
RETURNS varchar(1000)   
BEGIN   
DECLARE fid varchar(100) default '';   
DECLARE str varchar(1000) default rootId;   
  
WHILE rootId is not null do   
    SET fid =(SELECT pid FROM tree WHERE id = rootId);   
    IF fid is not null THEN   
        SET str = concat(str, ',', fid);   
        SET rootId = fid;   
    ELSE   
        SET rootId = fid;   
    END IF;   
END WHILE;   
return str;  
END

select * from tree where FIND_IN_SET(id, GET_PARENT_NODE(5));

public class TreeNodeDTO {
    
    private String id;
    private String parentId;
    private String name;
    private List<TreeNodeDTO> children = new ArrayList<>();
    public void add(TreeNodeDTO node) {
        if ("0".equals(node.parentId)) {
            this.children.add(node);
        } else if (node.parentId.equals(this.id)) {
            this.children.add(node);
        } else {
         	//递归调用add()添加子节点
            for (TreeNodeDTO tmp_node : children) {
                tmp_node.add(node);
            }
        }
    }
 }

List<TreeNodeDTO> list = dbMapper.getNodeList();
ArrayList<TreeNodeDTO> rootNodes = new ArrayList<>();
Map<Integer, TreeNodeDTO> map = new HashMap<>();
for (TreeNodeDTO node :list) {
    map.put(node.getId(), node);
    Integer parentId = node.getParentId();
    // 判断是否有父节点 (没有父节点本身就是个父菜单)
    if (parentId.equals('0')){
        rootNodes.add(node);
        // 找出不是父级菜单的且集合中包括其父菜单ID
    } else if (map.containsKey(parentId)){
        map.get(parentId).getChildren().add(node);
    }
}

START WITH CONNECT BY PRIOR

CREATE TABLE `company_inf` (
  `ID` varchar(32) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `NAME` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `PARENT_ID` varchar(32) COLLATE utf8mb4_unicode_ci DEFAULT NULL
)

INSERT INTO company_inf VALUES ('1','总经理王大麻子','1');
INSERT INTO company_inf VALUES ('2','研发部经理刘大瘸子','1');
INSERT INTO company_inf VALUES ('3','销售部经理马二愣子','1');
INSERT INTO company_inf VALUES ('4','财务部经理赵三驼子','1');
INSERT INTO company_inf VALUES ('5','秘书员工J','1');
INSERT INTO company_inf VALUES ('6','研发一组组长吴大棒槌','2');
INSERT INTO company_inf VALUES ('7','研发二组组长郑老六','2');
INSERT INTO company_inf VALUES ('8','销售人员G','3');
INSERT INTO company_inf VALUES ('9','销售人员H','3');
INSERT INTO company_inf VALUES ('10','财务人员I','4');
INSERT INTO company_inf VALUES ('11','开发人员A','6');
INSERT INTO company_inf VALUES ('12','开发人员B','6');
INSERT INTO company_inf VALUES ('13','开发人员C','6');
INSERT INTO company_inf VALUES ('14','开发人员D','7');
INSERT INTO company_inf VALUES ('15','开发人员E','7');
INSERT INTO company_inf VALUES ('16','开发人员F','7');

  SELECT *
  FROM T_PORTAL_AUTHORITY
  START WITH ID='1'
  CONNECT BY PRIOR ID = PARENT_ID

CREATE FUNCTION getChild(parentId VARCHAR(1000))
RETURNS VARCHAR(1000)
BEGIN
    DECLARE oTemp VARCHAR(1000);
    DECLARE oTempChild VARCHAR(1000);
    SET oTemp = '';
    SET oTempChild =parentId;
    WHILE oTempChild is not null DO
        IF oTemp != '' THEN
            SET oTemp = concat(oTemp,',',oTempChild);
        ELSE
            SET oTemp = oTempChild;
        END IF;
        SELECT group_concat(ID) INTO oTempChild FROM company_inf where parentId<>ID and FIND_IN_SET(parent_id,oTempChild)>0;
    END WHILE;
RETURN oTemp;
END

SELECT * FROM company_inf WHERE FIND_IN_SET(ID,getChild('2'));