MyBatis多条件查询看这一篇就够了

一：使用动态SQL完成多条件查询

a:使用if+where实现多条件查询

首先场景需求，有 个年级和班级表，第一个要求是根据模糊查询姓名，和年龄大小进行条件查询，接口层方法

public  List  getStudentByIf(student stu);

其次是映射文件的配置

        select * from student
       
           
           and stuAge>#{stuAge}
       
             
                 and stuName LIKE '%' #{stuName} '%'
             

       

    

测试

studentDao dao = MyBatis.getSessionTwo().getMapper(studentDao.class);
        student stu = new student();
        stu.setStuName("z");
       // stu.setStuAge(19);
        List list=  dao.getStudentByIf(stu);
       
        for (student item:list) {
            System.out.println("----------"+item.getStuName());
        }  打印效果
----------zhangyu----------zy----------zy----------zhang

b：choose when 分类

这种方式和java中choose循环结构原理是一样的，判断多种情况，只要修改一下映射文件即可

接口 类

public List getAllStudentByLike(Map userMap);  //使用map作为参数

映射文件

        select * from student
        
        
            
                 stuName like CONCAT('%',#{stuName},'%')
            
            
                 stuAge> #{stuAge}
            
    1=1

        
        
    

结果

zhangyu
zy
zy
zhang

c:使用foreach完成复杂 查询，有三种方式，

第一种：传入的参数为数组类型

//传一组 xueshengID 
public List getStudentBystuId_foreach_array(Integer[] ints);




映射文件配置
 
    
        select * from student
        
        where stuId IN
        /*数组形式传入学生Id*/
        
              #{stu}
        
        
    

测试类

Integer[] ints = {2,3,4};
        List list = dao.getStudentBystuId_foreach_array(ints);
        for (student item:list) {
            System.out.println(item.getStuName());
        }

第二种：传入list集合

public List getStudentBystuId_foreach_list(List list);

    
        select * from student
        
            where stuId IN
        /*集合形式传入学生Id*/
        
            #{stu}
        
        
    

测试：

studentDao dao = MyBatis.getSessionTwo().getMapper(studentDao.class);
        Integer ints = 2;
        List list = new ArrayList();
        list.add(ints);
        List stulist = dao.getStudentBystuId_foreach_list(list);
        for (student item:stulist) {
            System.out.println(item.getStuName());
        }

第三种：根据Map集合

public List getStudentBystuId_foreach_map(Map stuMap);

    
        select * from student where stuId IN
        /*集合形式传入学生Id*/
            
            #{stu}
        
    

Map stumap = new HashMap();
        List listStuId = new ArrayList();
        listStuId.add(2);
        listStuId.add(3);
        listStuId.add(4);
        stumap.put("stuId",listStuId);
         List list = dao.getStudentBystuId_foreach_map(stumap);
        for (student item:list
             ) {
            System.out.println(item.getStuName());
        }

打印结果可以执行以下。

d;一对多的两种实现方式

主要是resultMapper里的配置不同

接口方法

public grade getGradeById(int gradeId);

映射文件配置

    
        
        
        
            
            
            
        
    
    
    
        
        
            
    

    
        select * from grade,student where grade.gradeId = student.stuGrade and gradeId = #{gradeId}
    
    
    
        select * from grade where gradeId=#{gradeId}
    

    
        select * from student where stuGrade = #{stuGrade}
    

        select * from grade,student where grade.gradeId = student.stuGrade and gradeId = #{gradeId}
    
    
    
        select * from grade where gradeId=#{gradeId}
    

    
        select * from student where stuGrade = #{stuGrade}
    

@Test
    public void  TestConn(){
       gradeDao dao = MyBatis.getSessionTwo().getMapper(gradeDao.class);

       grade grade = dao.getGradeById(1);
       for (student item:grade.getGatStudent()            ) {
           System.out.println(item.getStuName());
       }

    }

两种方式都能实现，打印效果

方案一打印效果

==> Preparing: select * from grade,student where grade.gradeId = student.stuGrade and gradeId = ? ============一条sql
==> Parameters: 1(Integer)
<== Columns: gradeId, gradeName, stuId, stuName, stuAge, stuGrade
<== Row: 1, S1297, 2, zhangyu, 19, 1
<== Row: 1, S1297, 3, zy, 20, 1
<== Row: 1, S1297, 4, zy, 21, 1
<== Total: 3
zhangyu
zy
zy

Process finished with exit code 0

方案二打印效果

==> Preparing: select * from grade where gradeId=? ==========第一条sql
==> Parameters: 1(Integer)
<== Columns: gradeId, gradeName
<== Row: 1, S1297
====> Preparing: select * from student where stuGrade = ? ==========第二条sql
====> Parameters: 1(Long)
<==== Columns: stuId, stuName, stuAge, stuGrade
<==== Row: 2, zhangyu, 19, 1
<==== Row: 3, zy, 20, 1
<==== Row: 4, zy, 21, 1
<==== Total: 3
<== Total: 1
zhangyu
zy
zy

Process finished with exit code 0