mybatis多表查询多对多

浅浅的花香味﹌ 2021-10-19 12:32 447阅读 0赞

多对多查询就是两个实体类 通过一个中间表 来实现多对多查询 他和一对多有点类似。

<resultMap id="reMap" type="com.qst.domian.Employee">
            
            <id property="id" column="id"></id>
            <result property="Username" column="username"></result>
            <result property="gender" column="gender"></result>
    
            <collection property="roles" ofType="com.qst.domian.Role">
                <id property="roleId" column="roel_id"></id>
                <result property="roleName" column="role_name"></result>
                <result property="roleDesc" column="role_desc"></result>
            </collection>
        </resultMap>
        <select id="findRE" resultMap="reMap">
              select * from employee e left join user_role ur on e.id = ur.uid left  join role r on r.role_id = ur.uid;
        </select>

<resultMap id="roleMap" type="com.qst.domian.Role">
    
            <id property="roleId" column="role_id"></id>
            <result property="roleName" column="role_name"></result>
            <result property="roleDesc" column="role_desc"></result>
            <collection property="employees" ofType="com.qst.domian.Employee">
                <id property="id" column="id"></id>
                <result property="Username" column="username"></result>
                <result property="gender" column="gender"></result>
            </collection>
    
        </resultMap>
        <select id="findAll" resultMap="roleMap">
             select * from role r left join user_role ur on r.role_id = ur.uid left  join employee e on e.id = ur.uid;
        </select>