一对多的三种方式和多对一

Posted 2020-10-08 donghongbo

<!-- 对象级联 -->
    <resultMap type="Emp" id="emplist1">
        <id property="empno" column="EMPNO"/>
        <result property="ename" column="ENAME"/>
        <result property="job" column="JOB"/>
        <result property="mgr" column="MGR"/>
        <result property="hiredate" column="HIREDATE"/>
        <result property="sal" column="SAL"/>
        <result property="comm" column="COMM"/>
        <result property="deptno" column="DEPTNO"/>
        <result property="sex" column="SEX"/>
        <result property="dept.dno" column="DNO"/>
        <result property="dept.dname" column="DNAME"/>
        <result property="dept.loc" column="LOC"/>
    </resultMap>

<!-- 关联 -->
    <resultMap type="Emp" id="emplist2">
        <id property="empno" column="EMPNO"/>
        <result property="ename" column="ENAME"/>
        <result property="job" column="JOB"/>
        <result property="mgr" column="MGR"/>
        <result property="hiredate" column="HIREDATE"/>
        <result property="sal" column="SAL"/>
        <result property="comm" column="COMM"/>
        <result property="deptno" column="DEPTNO"/>
        <result property="sex" column="SEX"/>
        <association property="dept" resultMap="deptlist"></association>
    </resultMap>
    <resultMap type="Dept" id="deptlist">
        <result property="dno" column="DNO"/>
        <result property="dname" column="DNAME"/>
        <result property="loc" column="LOC"/>
    </resultMap> 

<!-- 关联查询 -->·
    <!-- <resultMap type="Emp" id="emplist3">
        <association property="dept" column="DEPTNO" select="mapper.DeptMapper.selectDept"></association>
    </resultMap>
    <select id="selectAllEmp" resultMap="emplist3">
        select * from p_emp e 
    </select> -->

多对一

<resultMap type="Dept" id="deptSelect">
        <id    property="dno" column="dno"/>
        <collection property="emp" column="dno" select="mapper.EmpMapper.selectOneEmp"/>
    </resultMap>
    <select id="selectDept" parameterType="Integer" resultMap="deptSelect">
        select * from p_dept d where d.dno=#{dno}
    </select>