<!--一对多单向的连接两表的查询-->

<resultMap type="Dept" id="deptMapper">

    <id property="deptNo" column="deptNo"/>

    <result property="deptName" column="deptName"/>

    <collection property="emps" ofType="Emp">

    <id property="empNo" column="empNo"/>

    <result property="empName" column="empName"/>

    </collection>

</resultMap>

<sql id="columns">

  dept.deptNo,deptName,empNo,empName

</sql>

<select id="findDeptInfoById" resultMap="deptMapper">

   select <include refid="columns"/> from dept,emp

   where dept.deptNo=emp.deptNo and dept.deptNo=#{deptNo}

</select> 

package cn.hmy.dao;

import cn.hmy.entity.Dept;

public interface DeptDao {

    //根据编号查询部门信息

    public Dept findDeptInfoById(Dept dept);

}

package cn.hmy.test;

import java.io.IOException;

import java.util.List;

import org.apache.ibatis.session.SqlSession;

import org.junit.Before;

import org.junit.Test;

import cn.hmy.dao.DeptDao;

import cn.hmy.entity.Dept;

import cn.hmy.util.MyBatisUtil;

public class MyTest {

    DeptDao deptDao;

    @Before

    public void myBefore(){

        SqlSession session = MyBatisUtil.getSession();

        deptDao = session.getMapper(DeptDao.class);

    }

    /**

     * 根据编号查找部门信息

     * @throws IOException

     */

    @Test

    public void findDeptInfoById() throws IOException{

        Dept dept=new Dept();

        dept.setDeptNo(3);

        Dept dept2 = deptDao.findDeptInfoById(dept);

        System.out.println(dept2);

    }

}

<!--一对多单向的单张表的查询  -->

<select id="selectEmpByDeptNo" resultType="Emp">

  select empNo,empName from Emp where deptNo=#{deptNo}

</select>

<sql id="columns">

deptNo,deptName

</sql>

<resultMap type="Dept" id="deptMapper">

   <id property="deptNo" column="deptNo"/>

    <result property="deptName" column="deptName"/>

    <collection property="emps" ofType="Emp"

     select="selectEmpByDeptNo"

     column="deptNo"

    />

</resultMap>

<select id="findDeptInfoById" resultMap="deptMapper">

select <include refid="columns"/> from Dept

where deptNo=#{deptNo}

</select>

<!-- 一对多单向的连接两表的查询 -->

<resultMap type="Emp" id="empMapper">

    <id property="empNo" column="empNo"/>

    <result property="empName" column="empName"/>

    <association property="dept" javaType="Dept">

      <id property="deptNo" column="deptNo"/>

      <result property="deptName" column="deptName"/>

    </association>

</resultMap>

<sql id="columns">

  dept.deptNo,deptName,empNo,empName

</sql>

<select id="findEmpById" resultMap="empMapper">

   select <include refid="columns"/> from dept,emp

   where dept.deptNo=emp.deptNo and empNo=#{empNo}

</select>

package cn.hmy.dao;

import cn.hmy.entity.Emp;

public interface EmpDao {

    //根据员工编号查找员工信息

    public Emp findEmpById(Emp emp);

}

package cn.hmy.test;

import java.io.IOException;

import java.util.List;

import org.apache.ibatis.session.SqlSession;

import org.junit.Before;

import org.junit.Test;

import cn.hmy.dao.EmpDao;

import cn.hmy.entity.Dept;

import cn.hmy.entity.Emp;

import cn.hmy.util.MyBatisUtil;

public class MyTest {

    EmpDao empDao;

    @Before

    public void myBefore(){

        SqlSession session = MyBatisUtil.getSession();

        empDao = session.getMapper(EmpDao.class);

    }

    /**

     * 根据员工编号查找员工信息

     * @throws IOException

     */

    @Test

    public void findEmpById() throws IOException{

        Emp emp=new Emp();

        emp.setEmpNo(2);

        Emp emp2 = empDao.findEmpById(emp);

        System.out.println(emp2);

    }

}

<!-- 多对一单向的连接单表的查询 -->

<select id="selectDeptInfoBydeptNo" resultType="Dept">

  select deptNo,deptName from dept where deptNo=#{deptNo}

</select>

<resultMap type="Emp" id="empMapper">

    <id property="empNo" column="empNo"/>

    <result property="empName" column="empName"/>

    <association property="dept" javaType="Dept"

       select="selectDeptInfoBydeptNo"

       column="deptNo"

    />

</resultMap>

<sql id="columns">

  empNo,empName,deptNo

</sql>

<select id="findEmpById" resultMap="empMapper">

   select <include refid="columns"/> from emp

   where empNo=#{empNo}

</select>