数据库表设计中涉及的递归查询解决思路

1、数据表的设计

CREATE TABLE work_query_dict
(
    id int primary key NOT NULL COMMENT '编号',
    title varchar(100) NOT NULL COMMENT '标签名',    
    parent_id int DEFAULT 0 COMMENT '父级编号',
    create_user varchar(64)  COMMENT '创建者',
    create_time  timestamp  DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
    update_user varchar(64)  COMMENT '更新者',
    update_time  timestamp  DEFAULT CURRENT_TIMESTAMP  COMMENT '更新时间',
    del_flag int DEFAULT 0 NOT NULL COMMENT '删除标记'
) 

2、控制层

/**
 * 查询工单查询的字典列表
 * @param
 * @return
 */
@RequestMapping("/findWorkQueryDictList")
@ResponseBody
public RestfulResponse findDictList(@RequestParam Map<String,Object> params, HttpServletRequest request){
    int id = Utils.parseInt(request.getParameter("id"),0);
    List<Map<String, Object>> dictList= workQueryDictService.findDictList();
    return RestfulResponse.success(dictList);
}

3、业务层

 @Override
    public List<Map<String, Object>> findDictList() {
        List<WorkQueryDict> treeMenu = workQueryDictDao.findWorkQueryDictByPid(0);
        List<Map<String, Object>> list = new ArrayList<>();
        if (treeMenu.size() > 0) {
            for (WorkQueryDict dict : treeMenu) {
                Map<String, Object> map = new LinkedHashMap<>();
                map.put("id", dict.getId());
                map.put("title", dict.getTitle());
                map.put("children", getChildren(dict.getId()));
                list.add(map);
            }
        }
        return list;
    }

/**
 * 获取孩子节点
 * @param id
 * @return
 */
private List<Object> getChildren(int id) {
    List<Object> list = new ArrayList<>();
    List<WorkQueryDict> treeMenu = workQueryDictDao.findWorkQueryDictByPid(id);
    for (WorkQueryDict dict : treeMenu) {
        Map<String, Object> map = new LinkedHashMap<>();
        map.put("id", dict.getId());
        map.put("title", dict.getTitle());
        map.put("children", getChildren(dict.getId()));
        list.add(map);
    }
    return list;
}

4、dao层

<resultMap id="workQueryDictMapping" type="csg.ios.zzfw.entity.WorkQueryDict">
        <result column="id" property="id"/>
        <result column="title" property="title"/>
        <result column="parent_id" property="parentId"/>
        <result column="create_user" property="createUser"/>
        <result column="create_time" property="createTime"/>
        <result column="update_user" property="updateUser"/>
        <result column="update_time" property="updateTime"/>
        <result column="del_flag" property="delFlag"/>
    </resultMap>

<select id="findWorkQueryDictByPid" parameterType="csg.ios.zzfw.entity.WorkQueryDict" resultMap="workQueryDictMapping">

    select id,title,parent_id,create_user,create_time,update_user,update_time from  work_query_dict
    <where>
        parent_id = #{id}
    </where>
</select>

</mapper>

5、展示的查询数据的结构：

一个树形结构