VIP23/04maven/mybatis/target/classes/EmployeeMapper.xml

<?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="com.sf.mapper.EmployeeMapper">

    <select id="getEmployeeinfo" parameterType="integer" resultType="employee">
        select * from employee where emp_id = #{empId}
    </select>

<!--
一对多用  <collection>
多对一用  <association>   javaType  是映射实体类的全类名
resultMap="map2"  <====>    <resultMap id="map2">     一一对应
 -->
    
    <resultMap id="map2" type="employee">
        <id column="emp_id" property="empId"></id>
        <result column="emp_name" property="empName"></result>
        <result column="salary" property="salary"></result>
        <association property="department" javaType="department">
            <id column="dept_id" property="deptId"></id>
            <result column="dept_name" property="deptName"></result>
        </association>
     </resultMap>
    
    <select id="getEmployeeinfoWithDepartment" parameterType="integer" resultMap="map2">
        select *
        from employee t1,
             department t2
        where t1.dept_id = t2.dept_id 
        and t1.emp_id = #{empId};
    </select>

</mapper>