mybatis一对多查询
一、一对多查询A表与B表是一对多关系:A表aad11B表ba_id112131A表对应的实体类EntityA,B表对应的实体类EntityBpublic class EntityA {private Integer a;private Integer ad;}public class EntityB{private Integer b;private Integer aId;}public cla
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一、一对多查询
A表与B表是一对多关系:
A表
a | ad |
---|---|
1 | 1 |
B表
b | a_id |
---|---|
1 | 1 |
2 | 1 |
3 | 1 |
A表对应的实体类EntityA,B表对应的实体类EntityB
public class EntityA {
private Integer a;
private Integer ad;
}
public class EntityB{
private Integer b;
private Integer aId;
}
public class EntityAVo {
private Integer a;
private Integer ad;
private List<EntityB> alist;
}
mybatis文件
<resultMap id="aMap" type="EntityAVo">
<result property="a" column="a"/>
<result property="ad" column="ad"/>
<collection property="alist" ofType="EntityB">
<result column="b" property="b"/>
<result column="a_id" property="aId"/>
</collection>
</resultMap>
<select id="test" resultMap="aMap">
SELECT
A.a,
A.ad,
B.b,
B.a_id
FROM
A
LEFT JOIN B ON B.a_id = A.a
</select>
返回的实体结构
EntityAVo
a=1
ad=1
alist=List<EntityB>
b=1,aId=1
b=2,aId=1
b=3,aId=1
例如下图
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