<!-- 查询所有订单信息 -->

    <select id="findOrdersList" resultType="cn.itcast.mybatis.po.OrdersCustom">

    SELECT

    orders.*,

    user.username,

    user.address

    FROM

    orders,    user

    WHERE orders.user_id = user.id

    </select>

<!-- 查询订单关联用户信息使用resultmap -->

    <resultMap type="cn.itheima.po.Orders" id="orderUserResultMap">

        <id column="id" property="id"/>

        <result column="user_id" property="userId"/>

        <result column="number" property="number"/>

        <result column="createtime" property="createtime"/>

        <result column="note" property="note"/>

        <!-- 一对一关联映射 -->

        <!--

        property:Orders对象的user属性

        javaType：user属性对应 的类型

         -->

        <association property="user" javaType="cn.itcast.po.User">

            <!-- column:user表的主键对应的列  property：user对象中id属性-->

            <id column="user_id" property="id"/>

            <result column="username" property="username"/>

            <result column="address" property="address"/>

        </association>

    </resultMap>

    <select id="findOrdersWithUserResultMap" resultMap="orderUserResultMap">

        SELECT

            o.id,

            o.user_id,

            o.number,

            o.createtime,

            o.note,

            u.username,

            u.address

        FROM

            orders o

        JOIN `user` u ON u.id = o.user_id

    </select>

<resultMap type="cn.itheima.po.user" id="userOrderResultMap">

        <!-- 用户信息映射 -->

        <id property="id" column="id"/>

        <result property="username" column="username"/>

        <result property="birthday" column="birthday"/>

        <result property="sex" column="sex"/>

        <result property="address" column="address"/>

        <!-- 一对多关联映射 -->

        <collection property="orders" ofType="cn.itheima.po.Orders">

            <id property="id" column="oid"/>

              <!--用户id已经在user对象中存在，此处可以不设置-->

            <!-- <result property="userId" column="id"/> -->

            <result property="number" column="number"/>

            <result property="createtime" column="createtime"/>

            <result property="note" column="note"/>

        </collection>

    </resultMap>

    <select id="getUserOrderList" resultMap="userOrderResultMap">

        SELECT

        u.*, o.id oid,

        o.number,

        o.createtime,

        o.note

        FROM

        `user` u

        LEFT JOIN orders o ON u.id = o.user_id

    </select>