mysql查询树类型的层级数据（⽗⼦，层层递归）⼀、创建表
CREATE TABLE `sys_station` (
`row_id` int NOT NULL AUTO_INCREMENT COMMENT '主键',
`project_id` int DEFAULT NULL,
`name` varchar(32) COLLATE utf8mb4_general_ci DEFAULT NULL,
`code` varchar(32) COLLATE utf8mb4_general_ci DEFAULT NULL,
mysql创建表数据类型`alias` varchar(32) COLLATE utf8mb4_general_ci DEFAULT NULL,
`type` tinyint DEFAULT NULL,
`latitude` double DEFAULT NULL COMMENT '纬度',
`longitude` double DEFAULT NULL COMMENT '经度',
`parent_id` int DEFAULT NULL,
`img_url` varchar(32) COLLATE utf8mb4_general_ci DEFAULT NULL,
`remark` varchar(32) COLLATE utf8mb4_general_ci DEFAULT NULL,
`created_by` int NOT NULL COMMENT '记录创建⼈',
`created_time` datetime DEFAULT NULL COMMENT '记录创建时间',
`updated_by` int NOT NULL COMMENT '记录修改⼈',
`updated_time` datetime DEFAULT NULL COMMENT '记录修改时间',
`version` int NOT NULL COMMENT '记录修改次数',
`is_deleted` tinyint NOT NULL COMMENT '逻辑删除标识',
PRIMARY KEY (`row_id`)
) ENGINE=InnoDB AUTO_INCREMENT=10 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci COMMENT='站点';
⼆、实体类
package com.basic.ity.device;
import batisplus.annotation.TableField;
import batisplus.annotation.TableName;
import com.basic.bean.BaseEntity;
import lombok.Data;
import lombok.EqualsAndHashCode;
import java.util.List;
/**
* 站点表
*/
@Data
@TableName("sys_station")
@EqualsAndHashCode(callSuper = true)
public class Station extends BaseEntity<Integer, Station> {
/**
* 编码
*/
private Integer projectId;
/**
* 站点编码
*/
private String code;
/
**
* 站点名称
*/
private String name;
/**
* 站点别名
*/
private String alias;
private String alias;
/**
* 编码
*/
private Integer type;
/**
* 纬度
*/
private Double latitude;
/**
* 经度
*/
private Double longitude;
/**
* ⽗id
*/
private Integer parentId;
/**
* 编码
*/
private String imgUrl;
/**
* 描述
*/
private String remark;
/
**
* ⼦集站点信息
*/
@TableField(exist = false)
List<Station> subStation;
}
三、xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-////DTD Mapper 3.0//EN"
"/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.basic.dule.system.dao.device.StationMapper">
<resultMap id="stationMap" type="com.basic.ity.device.Station">
<id column="row_id" property="rowId"></id>
<result column="project_id" property="projectId"></result>
<result column="name" property="name"></result>
<result column="code" property="code"></result>
<result column="alias" property="alias"></result>
<result column="type" property="type"></result>
<result column="latitude" property="latitude"></result>
<result column="longitude" property="longitude"></result>
<result column="parent_id" property="parentId"></result>
<result column="img_url" property="imgUrl"></result>
<result column="remark" property="remark"></result>
<collection property="subStation" column="row_id"  select="queryStationInfoByCondition"></collection>    </resultMap>
<select id="queryStationInfoByCondition" resultMap="stationMap">
select * from sys_station where parent_id = #{rowId}
</select>
</mapper>
四、Dao层
package com.basic.dule.system.dao.device;
import apper.BaseMapper;
import com.basic.ity.device.Station;
import org.apache.ibatis.annotations.Param;
import java.util.List;
public interface StationMapper extends BaseMapper<Station> {
List<Station> queryStationInfoByCondition(@Param("rowId") Integer rowId); }
好了，到此，代码完成，可以直接调⽤Dao层⽅法去获取树型数分层据了。

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