mysql - 如何添加缺少数据组合的行并用 0 估算相应字段

Question

我有域名和月份的组合以及相应月份的总订单数。我想用 0 值来估算缺失的组合。在 Pyspark 中可以使用哪些最便宜的聚合命令来实现此目的？

我有以下输入表:

domain      month    year   total_orders
google.com  01       2017   20
yahoo.com   02       2017   30
google.com  03       2017   30
yahoo.com   03       2017   40
a.com       04       2017   50
a.com       05       2017   50
a.com       06       2017   50

预期输出:

domain      month    year   total_orders
google.com  01       2017   20
yahoo.com   02       2017   30
google.com  03       2017   30
yahoo.com   03       2017   40
a.com       04       2017   50
a.com       05       2017   50
a.com       06       2017   50
google.com  02       2017   0
google.com  04       2017   0
yahoo.com   04       2017   0
google.com  05       2017   0
yahoo.com   05       2017   0
google.com  06       2017   0
yahoo.com   06       2017   0

这里预期的输出顺序并不重要。

Answer 1

最简单的方法是合并每个域的所有月份和年份:

select my.year, my.month, d.domain, coalesce(t.total_orders, 0) as total_orders
from (select distinct month, year from input) my cross join
     (select distinct domain from input) d left join
     t
     on t.month = my.month and t.year = my.year and t.domain = d.domain;

注意:这假设每个年/月组合在数据中的某个位置至少出现一次。

获取某个范围内的值很痛苦，因为您已将日期拆分为多个列。让我假设年份都相同，如您的示例所示:

select my.year, my.month, d.domain, coalesce(t.total_orders, 0) as total_orders
from (select distinct month, year from input) my join
     (select domain, min(month) as min_month, max(month) as max_month
      from input
     ) d
     on my.month >= d.min_month and my.month <= d.max_month left join
     t
     on t.month = my.month and t.year = my.year and t.domain = d.domain