MyBatis学习（十四）——多对一和一对多查询

Love The Way You Lie 2022-12-29 09:28 148阅读 0赞

### 多对一查询和一对多查询 ###

*  多对一查询
 *   *  按照查询嵌套处理
     *  按照结果嵌套处理
 *  一对多查询
 *   *  实体类
     *  按结果查询
     *  按照查询嵌套处理

# 多对一查询 #

## 按照查询嵌套处理 ##

**查询所有的学生信息以及对应的老师的信息**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 1]  
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## 按照结果嵌套处理 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 3]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 4]  
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# 一对多查询 #

一个老师拥有多个学生对于老师就是一对多

## 实体类 ##

package com.my.pojo;
    
    import lombok.Data;
    
    import java.util.List;
    
    @Data
    public class Teacher {
        
        private int id;
        private String name;
    
        //一个老师有多个学生
        private List<Student> students;
    }

package com.my.pojo;
    
    import lombok.Data;
    
    @Data
    public class Student {
        
        private int id;
        private String name;
    
        private int tid;
    }

## 按结果查询 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 6]  
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## 按照查询嵌套处理 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoYXJfbQ_size_16_color_FFFFFF_t_70 8]  
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