<?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">
<!-- 命名空間 xml與dao的連接 -->
<mapper namespace="com.aaa.dao.EmpMapper">
<resultMap type="emp" id="empMap">
<id column="empno" property="empno"/>
<association column="deptno" property="dept" javaType="dept">
<id column="deptno" property="deptno"/>
</association>
</resultMap>
<select id="selectManytoOne" parameterType="int" resultMap="empMap">
select
e.empno,e.ename,e.job,e.mgr,e.hiredate,e.sal,e.comm,
e.deptno,d.dname,d.loc
from emp e left join dept d on e.deptno=d.deptno
where d.deptno=#{deptno}
</select>
</mapper>
原因在於個別開發者或同學沒有寫主表的empno, 會出現查詢結果有數據,但是結果只有一條的情況。