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sql - 使用 max() 和 group by 后获取多行

问题描述

我正在尝试根据具有最活跃属性xml_id的任何一个段将一个段分配给一个。我已经为此编写了一个查询：xml_id

我正在使用这样的选择创建一个表：

create table schema.table4 as
select
    yyyy_mm_dd,
    xml_id,
    segment as xml_segment,
    max(property_count)
from(
    select
        t1.yyyy_mm_dd,
        t2.xml_id,
        t3.segment,
        count(t1.hotel_id) as property_count
    from(
        select
            yyyy_mm_dd,
            hotel_id
        from
            schema.table1
        where
            is_active = 1
            and yyyy_mm_dd = "2020-10-01"
    ) t1
    left join(
        select
            yyyy_mm_dd,
            hotel_id,
            xml_id
        from
            schema.table2
        where
            yyyy_mm_dd = "2020-10-01"
            and xml_id is not null
    ) t2 on t2.hotel_id = t1.hotel_id and t2.yyyy_mm_dd = t1.yyyy_mm_dd
    inner join
        schema.table3 t3 on t3.hotel_id = t1.hotel_id
    group by
        1,2,3
) x
group by
    1,2,3

但是，当我查询此表时，我可以看到每个xml_id. 我本来预计只会MAX()插入带有 property_count 的段。怎么不是这样？

select
    xml_id, count(*)
from
    schema.table4

显示多行，其中xml_id有两行和三行。我需要它只有一行，段应该是最高的那一个property_count。

下面的一些示例输出。xml_id继承它具有最多属性的段。

t1：

| yyyy_mm_dd | hotel_id | is_active |
|------------|----------|-----------|
| 2020-10-01 | 1        | 1         |
| 2020-10-01 | 2        | 1         |
| 2020-10-01 | 3        | 1         |
| 2020-10-01 | 4        | 1         |
| 2020-10-01 | 5        | 1         |
| 2020-10-01 | 6        | 1         |
| 2020-10-01 | 7        | 0         |

t2：

| yyyy_mm_dd | hotel_id | xml_id |
|------------|----------|--------|
| 2020-10-01 | 1        | 444    |
| 2020-10-01 | 2        | 444    |
| 2020-10-01 | 3        | 444    |
| 2020-10-01 | 4        | 920    |
| 2020-10-01 | 5        | 920    |
| 2020-10-01 | 6        | 920    |
| 2020-10-01 | 7        | null   |

t3：

| hotel_id | segment |
|----------|---------|
| 1        | Home    |
| 2        | Core    |
| 3        | Core    |
| 4        | Core    |
| 5        | Home    |
| 6        | Home    |
| 7        | Chain   |

预期输出：

| yyyy_mm_dd | xml_id | segment |
|------------|--------|---------|
| 2020-10-01 | 444    | Core    |
| 2020-10-01 | 920    | Home    |

标签： sqlhivehiveql

解决方案

如果我理解正确，您想按日期计算活动的数量，xml_id并且segment. 这是此计数的基本查询：

select t2.yyyy_mm_dd, t2.xml_id, t3.segment, count(*) as num_actives
from t2 join
     t1
     on t2.hotel_id = t1.hotel_id and
        t2.yyyy_mm_dd  = t1.yyyy_mm_dd join
     t3
     on t3.hotel_id = t2.hotel_id
where t1.is_active = 1
group by t2.yyyy_mm_dd, t2.xml_id, t3.segment;

要获得最高值，您可以使用窗口函数：

select t.*
from (select t2.yyyy_mm_dd, t2.xml_id, t3.segment, count(*) as num_actives,
             row_number() over (partition by t2.yyyy_mm_dd, t2.xml_id order by count(*) desc) as seqnum
      from t2 join
           t1
           on t2.hotel_id = t1.hotel_id and
              t2.yyyy_mm_dd  = t1.yyyy_mm_dd join
           t3
           on t3.hotel_id = t2.hotel_id
      where t1.is_active = 1
      group by t2.yyyy_mm_dd, t2.xml_id, t3.segment
     ) t
where seqnum = 1;

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