Mybatis resultMap灵活用法（使用子查询）

### 背景
查询广州每个景点的总流量，和每个景点每日流量

#### 数据表 t_广州
|唯一标识id|地点place|流量counts|日期date|
|:---:|:---:|:---:|:---:|
|1|动物园|100|'2018-11-11'|
|2|动物园|200|'2018-11-12'|
|3|植物园|100|'2018-11-11'|

### 需求
统计每个地点的总流量，和每天的流量
结果示意结构如下：
````json
{
place: '动物园',
allCounts: 300,
perDay : [
{
date: '2018-11-11',
counts: 100
},
{
date: '2018-11-12',
counts: 200
}
]
},
{
place: '植物园',
allCounts: 100,
perDay : [
{
date: '2018-11-11',
counts: 100
}
]
},
````
xml文件如下：
````xml
<select id="pageResultMapSelect" parameterType="java.util.Map" resultMap="pageResultMap">
select date,counts from t_广州 where place=#{place} group by date
</select>
<resultMap id="pageResultMap" resultType="java.util.Map">
<result column="place" property="place" />
<result column="allCounts" property="allCounts" />
<collection property="perDay" javaType="java.util.List" ofType="java.util.Map" column="(place=place)" select="pageResultMapSelect"></collection>
</resultMap>
<select id="page" parameterType="java.util.Map" resultMap="pageResultMap">
select place,sum(counts) as allCounts from t_广州 group by place
</select>
````