Mybatis 004 ResultMap及多表联查

简单的ResultMap

 

    
    
    
    


    SELECT * FROM STUDENTS


    SELECT * FROM STUDENTS WHERE STUD_ID=#{studId}

resultMap的id就是为了方便sql语句映射的时候使用，resultMap对应的就是他的id，type就是真正返回的类型。

result是为了映射数据属性，column是数据库里的列名，property是POJO的属性名。

id是主键，column是数据库里的列名，property是POJO的属性名。

 

一对一映射

 

学生表

地址表

学生表中包含ADDR_ID字段指向地址表的ADDR_ID主键。

学生类：

public class Student
{
    private Integer studId;
    private String name;
    private String email;
    private PhoneNumber phone;
    private Address address;
    //setters & getters
}

地址类：

public class Address
{
    private Integer addrId;
    private String street;
    private String city;
    private String state;
    private String zip;
    private String country;
    // setters & getters
}

查询语句：

    SELECT STUD_ID, NAME, EMAIL, A.ADDR_ID, STREET, CITY, STATE, ZIP, COUNTRY FROM STUDENTS S LEFT OUTER JOIN ADDRESSES A ON S.ADDR_ID=A.ADDR_ID WHERE STUD_ID=#{studId}

映射关系：

 

一对多映射

 

教师表

课程表

 

一个教师对应多个课程，属于1：N的关系

课程类

public class Course
{
    private Integer courseId;
    private String name;
    private String description;
    private Date startDate;
    private Date endDate;
    private Integer tutorId;
    //setters & getters
}

教师类

public class Tutor
{
    private Integer tutorId;
    private String name;
    private String email;
    private Address address;
    private List courses;
    //setters & getters
}

教师类中使用List包含多个课程。

查询语句

    SELECT T.TUTOR_ID, T.NAME AS TUTOR_NAME, EMAIL, C.COURSE_ID, C.NAME, DESCRIPTION, START_DATE, END_DATE FROM TUTORS T LEFT OUTER JOIN ADDRESSES A ON T.ADDR_ID=A.ADDR_ID
LEFT OUTER JOIN COURSES C ON T.TUTOR_ID=C.TUTOR_ID WHERE T.TUTOR_ID=#{tutorId}

映射关系