SQL:运行不同值的总计数

我试图在一个窗口中获得唯一值的滚动数

我的桌子是这样的：

SELECT 
   user_id
   , order_date
   , product
FROM example_table 
WHERE user_id = 1 
ORDER BY order_date ASC

用户id 订单日期 产品 1. 2021-01-01 A. 1. 2021-01-01 B 1. 2021-01-04 A. 1. 2021-01-07 C 1. 2021-01-09 C 1. 2021-01-20 A.

---

对于每个项目，您可以记录它出现的最早日期。然后把这些加起来：

select et.* except (seqnum),
       countif(seqnum = 1) over (partition by user_id order by order_date) as running_distinct_count
from (select et.*,
             row_number() over (partition by user_id, product order by order_date) as seqnum
      from example_table et
     ) et

下面是BigQuery的示例

select * except(cum_products),
  (select count(distinct product) from t.cum_products product) as cum_dist_count
from (
    select *, 
      array_agg(product) over prev_rows as cum_products
    from example_table
    window prev_rows as (partition by user_id order by order_date)
) t   

如果应用于您问题中的样本数据

with example_table as (
  select 1 user_id, '2021-01-01' order_date, 'A' product union all
  select 1, '2021-01-02', 'B' union all
  select 1, '2021-01-04', 'A' union all
  select 1, '2021-01-07', 'C' union all
  select 1, '2021-01-09', 'C' union all
  select 1, '2021-01-20', 'A' 
) 

输出为

---

这正是我想要的-谢谢@格里泽克。如果这回答了你的问题，你可以接受答案。你有机会尝试吗？