MyBatis 多对一查询，级联实现

实体类：

• Dept.java

public class Dept {
	private int deptno;
	private String dname;
	private String loc;
	private List emps;
	//…… getter/setter方法
}

• Emp.java

public class Emp {
    private Integer empno;
    private String ename;
    private String job;
    private Integer mgr;
    private LocalDate hiredate;
    private BigDecimal sal;
    private BigDecimal comm;
    private Dept dept;  // 多对一：在多的一方添加一
	//getter/setter方法、默认构造方法、去除dept属性的全参构造方法及toString()方法
}

EmpMapper.java

@Mapper
public interface EmpMapper {
    // 查询指定编号员工的详细信息，包括所在部门的详细信息
    Emp getEmp(@Param("empno") Integer empno);
}

EmpMapper.xml

    
        
        
        
        
        
        
        
        
        
        
        
    
    
        select empno,ename,job,mgr,hiredate,sal,comm,
               dept.deptno dno,dept.dname,dept.loc
        from tb_emp emp
                     left join tb_dept dept on emp.deptno = dept.deptno
        where empno = #{empno}
    

测试代码

@SpringBootTest
public class EmpMapperTest {
    @Resource
    private EmpMapper empMapper;
    @Test
    void getEmp(){
        Emp emp = empMapper.getEmp(7788);
        System.out.println(emp);
    }
}