Mybatis使用collection映射一对多查询分页问题详解
作者：小柒v
本文通过修改SQL查询语句,解决了在分页条件下关联查询多表时,多的一端数据不正确的问题,从而实现了正常的展示
Mybatis使用collection映射一对多查询分页
场景
页面展示列表，需要关联查询另外1张表多的字段，分页。
/**
* 标签
*/
private List<BasicResidentTags> tags;
@Data
@TableName("basic_resident_tags")
public class BasicResidentTags{
private static final long serialVersionUID=1L;
/**
* 标签id
*/
@TableId(value = "id",type = IdType.AUTO)
private Integer id;
/**
* 名称
*/
private String name;
/**
* 颜色
*/
private String color;
/**
* 居民id
*/
private Integer residentId;
}
原来的sql这样写
<!--一对多映射-->
<resultMap id="many" type="com.vkl.basic.domain.vo.admin.BasicResidentListVo">
<id property="residentId" column="resident_id"/>
<result property="name" column="name"/>
<result property="sex" column="sex"/>
<result property="houseHolder" column="house_holder"/>
<result property="residentName" column="resident_name"/>
<result property="outsider" column="outsider"/>
<result property="room" column="room"/>
<collection property="tags" ofType="com.vkl.basic.domain.BasicResidentTags">
<id column="tagsId" property="id"></id>
<result column="tagsName" property="name"></result>
<result column="color" property="color"></result>
<result column="tid" property="residentId"></result>
</collection>
</resultMap>
<select id="selectPageList" resultType="com.vkl.basic.domain.vo.admin.BasicResidentListVo" resultMap="many"
parameterType="com.vkl.basic.domain.bo.admin.BasicResidentAdminBo">
select b.resident_id,b.`name`,b.sex,b.house_holder,b.resident_name,b.outsider,b.room,
t.id as tagsId,t.`name` as tagsName,t.color,t.resident_id as tid
from basic_resident b LEFT JOIN basic_resident_tags t
on b.resident_id = t.resident_id
where del_flg = '0'
<if test="param.name != null and param.name != ''">
and b.name like concat('%',#{param.name},'%')
or
b.resident_name like concat('%',#{param.name},'%')
</if>
<if test="param.tags != null and param.tags != ''">
and t.name = #{param.tags}
</if>
order by b.resident_id
limit #{query.pageNum},#{query.pageSize}
</select>
正常查询tags有两条
加上分页条件，多的一端只有一条数据。
修改之后的sql
分页满足正常展示多的一端。
<!--一对多映射-->
<resultMap id="many" type="com.vkl.basic.domain.vo.admin.BasicResidentListVo">
<id property="residentId" column="resident_id"/>
<result property="name" column="name"/>
<result property="sex" column="sex"/>
<result property="houseHolder" column="house_holder"/>
<result property="residentName" column="resident_name"/>
<result property="outsider" column="outsider"/>
<result property="room" column="room"/>
<collection property="tags" ofType="com.vkl.basic.domain.BasicResidentTags"
column="tid" select="selectTagsByResidentId">
</collection>
</resultMap>
<!--主查询条件-->
<select id="selectPageList" resultType="com.vkl.basic.domain.vo.admin.BasicResidentListVo" resultMap="many"
parameterType="com.vkl.basic.domain.bo.admin.BasicResidentAdminBo">
select b.resident_id,b.`name`,b.sex,b.house_holder,b.resident_name,b.outsider,b.room,
t.id as tagsId,t.`name` as tagsName,t.color,t.resident_id as tid
from basic_resident b LEFT JOIN basic_resident_tags t
on b.resident_id = t.resident_id
where del_flg = '0'
<if test="param.name != null and param.name != ''">
and b.name like concat('%',#{param.name},'%')
or
b.resident_name like concat('%',#{param.name},'%')
</if>
<if test="param.tags != null and param.tags != ''">
and t.name = #{param.tags}
</if>
order by b.resident_id
limit #{query.pageNum},#{query.pageSize}
</select>
<!--子查询-->
<select id="selectTagsByResidentId" resultType="com.vkl.basic.domain.BasicResidentTags">
select * from basic_resident_tags where resident_id=#{tid}
</select>
总结
以上为个人经验，希望能给大家一个参考，也希望大家多多支持脚本之家。