Sql 有效的多群by

我有下表：

年 周 第一天 第二天 第3天 2020 1. 步行 跳跃 游 2020 3. 步行 游 步行 2020 1. 跳跃 步行 游

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您需要查找

distinct

事件，对表执行

交叉连接

，并使用

条件聚合

，如下所示：

select t.year, t.week, e.event, 
       count(case when t.day_1 = e.event then 1 end) as count_day_1,
       count(case when t.day_2 = e.event then 1 end) as count_day_2,
       count(case when t.day_3 = e.event then 1 end) as count_day_3 
  from your_Table t
  cross join (select distinct day_1 as event from your_table
              union all select day_2 from your_table
              union all select day_3 from your_table) e
group by t.year, t.week, e.event

演示代码是MS SQL

如果要为每个事件每周和每年生成完整的网格，则需要两个预聚合，一个用于事件，另一个用于每年和每周

比如：

这将起作用，但由于在实际聚合发生之前需要对数据进行标准化，因此效率值得怀疑

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如果可能的话，我建议首先将表转换为3NF，只包含年、周、事件和日的关键列。然后可以生成一个相当有效的摘要。以提前正常化为代价。否则，查询中需要转换成本。

在BigQuery中，我将使用数组取消Pivot，然后聚合：

with t as (
       select 2020 as year, 1 as week, 'Walk' as day_1, 'Jump' as day_2, 'Swim' as day_3 union all
       select 2020, 3, 'Walk', 'Swim', 'Walk' union all
       select 2020, 1, 'Jump', 'Walk', 'Swim'
      )
select t.year, t.week, s.event,
       countif(day = 1) as day_1, countif(day = 2) as day_2, countif(day = 3) as day_3
from t cross join
     unnest([struct(t.day_1 as event, 1 as day),
             struct(t.day_2 as event, 2 as day),
             struct(t.day_3 as event, 3 as day)
            ]) s
group by t.year, t.week, s.event;
              

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考虑一下这个不那么冗长的选项

select year, week, event, 
  countif(offset = 0) as day_1, 
  countif(offset = 1) as day_2, 
  countif(offset = 2) as day_3
from `project.dataset.table`,
unnest([day_1, day_2, day_3]) event with offset
where not event is null
group by year, week, event   

如果应用于问题中的样本数据，则输出为

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作为一种可能的解决方案：附带条件聚合可能会有所帮助。源表中没有

事件

列，因此

交叉连接

右@astentx中应该有取消激励逻辑。已更新查询。请检查我是否已编辑，是否有效：1）e.day\u N应为t.day\u N；2） BigQuery查询

联合

并要求执行

选择distinct。。。联合所有人

。我很有趣！很难将带有insert into table变量的T-SQL内容移植到其他DBMS。您可以为此使用

with

子句，使其可移植到几乎所有SQL方言中，因此最好重写查询，使此答案在不重写代码的情况下或多或少有用

select year, week, event, 
  countif(offset = 0) as day_1, 
  countif(offset = 1) as day_2, 
  countif(offset = 2) as day_3
from `project.dataset.table`,
unnest([day_1, day_2, day_3]) event with offset
where not event is null
group by year, week, event