Question

我的问题类似于How to simulate a pivot table with BigQuery?。但是想象一下，你有不可预测的行数，所以你不能在IF语句中列出它们。那么有没有办法从一列中获取DISTINCT值并从中创建列列表？

Answer 1

以下非常简单的示例只是为了显示方法：

假设你有temp.example表：

false

并且，假设你想要构建如下所示的查询，但是事先不知道你有多少不同的类别

select * from
(select '2015-08-01' as day, 1 as category, 11 as volume),
(select '2015-08-01' as day, 2 as category, 21 as volume),
(select '2015-08-01' as day, 3 as category, 31 as volume),
(select '2015-08-02' as day, 1 as category, 101 as volume),
(select '2015-08-02' as day, 2 as category, 201 as volume),
(select '2015-08-03' as day, 1 as category, 301 as volume),
(select '2015-08-03' as day, 2 as category, 302 as volume),
(select '2015-08-03' as day, 4 as category, 304 as volume)

以下是完全符合此标准的GBQ代码

select 
   day,
   sum(if(category = 1, volume, 0)) as category_1,
   sum(if(category = 2, volume, 0)) as category_2,
   sum(if(category = 3, volume, 0)) as category_3,
   sum(if(category = 4, volume, 0)) as category_4
from temp.example
group by day
order by day

此查询的输出是一个查询，如果您运行它将为您生成枢轴

day          category_1  category_2 category_3   category_4  
2015-08-01           11          21         31            0  
2015-08-02          101         201          0            0  
2015-08-03          301         302          0          304

Answer 2

确实可以，但您需要使用自己的编程语言，因为您无法使用SQL查询语言生成SQL语法。

自动生成行中的列（无IF）

2 个答案: