MyBatis（四）关于多表联查 关联关系之一--------一对多（单条sql语句查询）

然后创建部门接口以及对应的xml文件

package dao;

import entity.Dept;
import entity.Emp;

import java.util.List;

/**
 * Created by mycom on 2018/2/26.
 */
public interface IDeptDao {
    //根据部门编号获得部门名称  员工名称  单条sql
    public Dept getEmpByDeptNo(int deptNo);
}

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="dao.IDeptDao">
    <resultMap id="deptMaper" type="Dept">
        <id column="d" property="deptNo"></id>
        <result column="deptName" property="deptName"></result>
        <collection property="emps" ofType="Emp">
            <id column="empNo" property="empNo"></id>
            <result column="empName" property="empName"></result>
        </collection>
    </resultMap>

    <!--查询部门和员工  单条sql语句方案-->
    <select id="getEmpByDeptNo" resultMap="deptMaper">
        SELECT dept.deptNo as d ,deptName,empName FROM dept,emp
        WHERE dept.`deptNo`=emp.`deptNo`
        AND dept.`deptNo`=#{deptNo}
    </select>

</mapper>

编写测试类

//查询部门和员工  单条sql
@Test
public void oneToMany(){
    SqlSession sqlSession = MyBatisUtil.getSession();
    IDeptDao mapper = sqlSession.getMapper(IDeptDao.class);
    Dept dept = mapper.getEmpByDeptNo(1);
    System.out.println("部门名称"+dept.getDeptName());
    for (Emp emp:dept.getEmps()) {
        System.out.println(emp.getEmpName());
    }
    sqlSession.close();
}

MyBatis（四）关于多表联查 关联关系之一--------一对多（单条sql语句查询）

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