使用mybatis的resultMap进行复杂查询

 

 

记录下mybatis的集合查询中碰到的问题

https://jaychang.iteye.com/blog/2357143

 

MyBatis ofType和javaType区别

https://blog.csdn.net/u013216156/article/details/78642920

 

mybatis 关联查询 resultMap 同名冲突

https://blog.csdn.net/caser_hdmi/article/details/75948091

 

使用mybatis的resultMap进行复杂查询

https://www.cnblogs.com/lesliehe/p/8206609.html

 

mybatis <collection>标签 类型为string时无法获取重复数据错误

https://www.cnblogs.com/lishuaiqi/p/10244274.html

 

使用resultMap进行一对多关联查询的方式有两种：

方法 1、 使用左连接查询所有关联数据

1.     <resultMap id="peopleResultMap" type="People">  

2.         <id property="id" column="id" />  

3.         <result property="name" column="name" />   

4.         <collection property="qqs" ofType="string" javaType="list">  

5.             <result column="qq" />  

6.         </collection>  

7.     </resultMap>  

8.       

9.     <select id="selectPeopleById" resultMap="peopleResultMap">  

10.         select p.*,pq.qq from  

11.         people p left join  people_qq pq on p.id = pq.people_id   

12.         where p.id = #{id}  

13.     </select>

 

如上面，左连接关联查询出qq表的qq字段，然后将qq通过resultMap的集合类放到这个List<String> qqs这个属性字段中。

优点：查询数据只需要查询一次就可以了。

缺点：因为左连接查询，people表一对多qq表，会查询出重复的id数据行。这样就无法使用到数据库自带的分页函数。

select p.*,pq.qq from  

         people p left join  people_qq pq on p.id = pq.people_id   

         where p.id = #{id} 

上面这个sql查询出来的数据格式

如下：

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" alt="" />

 

方法 2 使用子查询的方式查询

1.     <resultMap id="peopleResultMap" type="People">
2.         <id property="id" column="id" />
3.         <result property="name" column="name" />
4.         <collection property="qqs" ofType="string" javaType="list">
5.             <result column="qq" />
6.         </collection>
7.     </resultMap>
8.
9.     <select id="selectPeopleById" resultMap="peopleResultMap">
10.         select p.*,pq.qq from
11.         people p left join  people_qq pq on p.id = pq.people_id
12.         where p.id = #{id}
13.     </select>

 

子查询，就是在集合列表中调用另一个查询，进行数据赋值。

优点：可以使用数据库自带的分页函数

缺点：查询数据需要多次调用子查询进行集合字段数据查询。如果是大数据量查询，将会需要多次调用子查询sql。

 

mybatis默认使用懒加载的方式进行集合的子查询。存在问题。

可以查看下面这篇文章：mybatis问题解决

Springmvc+mybatis,mybatis配置延迟加载时，json序列化异常
https://ask.csdn.net/questions/344738?sort=comments_count

实体类有一个属性是其它实体类的类型，mybatis默认使用了 延迟加载，导致在处理这个类的时候某些属性不能被序列化，因此造成了上述原因
https://www.oschina.net/question/2312022_2232071
最近做项目时，使用了mybatis级联查询，配置了懒加载模式，结果通过springMvc返回json时报的错。报错如下：
https://blog.csdn.net/qq_33548914/article/details/79991280