MyBatis实现两个表联合查询：order_items和products

<resultMap id='BaseResultMap' type='com.ecommerce.book.pojo.Product'>
    <id property='id' column='id' jdbcType='INTEGER'/>
    <result property='name' column='name' jdbcType='VARCHAR'/>
    <result property='description' column='description' jdbcType='VARCHAR'/>
    <result property='price' column='price' jdbcType='DECIMAL'/>
    <result property='createdAt' column='created_at' jdbcType='TIMESTAMP'/>
    <result property='updatedAt' column='updated_at' jdbcType='TIMESTAMP'/>
</resultMap>

<sql id='Base_Column_List'>
    id,name,description,price,created_at,updated_at
</sql>

<select id='selectProductByOrderId' resultMap='BaseResultMap'>
    select p.id,p.name,p.description,p.price,p.created_at,p.updated_at
    from products p join order_items oi on p.id = oi.product_id
    where oi.order_id = #{orderId}
</select>