Emp getEmpById(@Param("id") Integer id);

　　<!--

        sql片段：可以记录一段sql，在需要用的地方使用include标签进行引用

    -->

    <sql id="empColumns">

        emp_id,emp_name,age,gender,dept_id

    </sql>

    <select id="getEmpById" resultType="com.xxx.dynamicSQL.entity.Emp">

        select <include refid="empColumns"></include>

        from t_emp

        where emp_id = #{id}

    </select>

@Test

    public void testGetEmpByid(){

        SqlSession sqlSession = SqlSessionUtil.getSqlSession();

        EmpMapper mapper = sqlSession.getMapper(EmpMapper.class);

        Emp emp = mapper.getEmpById(2);

        System.out.println(emp);

    }