在每行更改值时附上最近的时间戳

Question

我有更新属性的数据集：

user_id	flag	updated_at
123	1	101
123	0	101
123	1	102
123	1	103
123	1	104
124	0	101
124	0	102
124	0	110

我需要在 flag 值的最近更改时为每一行分配一个值，因此它应该如下所示：

user_id	flag	updated_at	recent_updated_at
123	1	101	101
123	0	102	102
123	1	103	103
123	1	104	103
123	1	105	103
124	0	101	101
124	0	102	101
124	0	110	101

到目前为止我有这个查询，但现在感觉卡住了：

with raw_dataset as (
            SELECT 123 as user_id, 1 as flag, 101 as updated_at
  UNION ALL SELECT 123 as user_id, 0 as flag, 102 as updated_at
  UNION ALL SELECT 123 as user_id, 1 as flag, 103 as updated_at
  UNION ALL SELECT 123 as user_id, 0 as flag, 104 as updated_at
  UNION ALL SELECT 123 as user_id, 0 as flag, 105 as updated_at
  UNION ALL SELECT 124 as user_id, 1 as flag, 101 as updated_at
  UNION ALL SELECT 124 as user_id, 1 as flag, 103 as updated_at
  UNION ALL SELECT 124 as user_id, 1 as flag, 110 as updated_at

)
, dataset as (
select * from (
  select 
    *, 
--    lag(flag, 1, -1) over (partition by user_id order by updated_at ASC) as lag_,
    row_number() over (partition by user_id, flag order by updated_at ASC) as rn
  from raw_dataset
  )
)
SELECT *, first_value(updated_at) over (partition by user_id,flag order by rn ASC) FROM dataset 
ORDER BY user_id, updated_at ASC

有什么想法、提示吗？提前致谢！

Answer 1

是你需要的吗

with raw_dataset as (
            SELECT 123 as user_id, 1 as flag, 101 as updated_at
  UNION ALL SELECT 123 as user_id, 0 as flag, 102 as updated_at
  UNION ALL SELECT 123 as user_id, 1 as flag, 103 as updated_at
  UNION ALL SELECT 123 as user_id, 0 as flag, 104 as updated_at
  UNION ALL SELECT 123 as user_id, 0 as flag, 105 as updated_at
  UNION ALL SELECT 124 as user_id, 1 as flag, 101 as updated_at
  UNION ALL SELECT 124 as user_id, 1 as flag, 103 as updated_at
  UNION ALL SELECT 124 as user_id, 1 as flag, 110 as updated_at

)
, dataset as (
  select *,
    row_number() over (partition by user_id order by updated_at ASC) 
    - row_number() over (partition by user_id, flag order by updated_at ASC) as grp
  from raw_dataset
)
SELECT *, min(updated_at) over (partition by user_id, flag, grp)
FROM dataset 
ORDER BY user_id, updated_at ASC

Answer 2

您似乎想要 flag 值更改的最近时间。你的问题比较混乱，因为问题中的数据与代码中的数据不同。

但是，请遵循returns问题中的数据和您想要的：

with raw_dataset as (
            SELECT 123 as user_id, 1 as flag, 101 as updated_at
  UNION ALL SELECT 123 as user_id, 0 as flag, 102 as updated_at
  UNION ALL SELECT 123 as user_id, 1 as flag, 103 as updated_at
  UNION ALL SELECT 123 as user_id, 1 as flag, 104 as updated_at
  UNION ALL SELECT 123 as user_id, 1 as flag, 105 as updated_at
  UNION ALL SELECT 124 as user_id, 0 as flag, 101 as updated_at
  UNION ALL SELECT 124 as user_id, 0 as flag, 103 as updated_at
  UNION ALL SELECT 124 as user_id, 0 as flag, 110 as updated_at
)
select rd.*,
       max(case when prev_flag is null or prev_flag <> flag then updated_at end) over (
            partition by user_id
            order by updated_at
           ) as most_recent_updated_at
from (select rd.*,
             lag(flag) over (partition by user_id order by updated_at) as prev_flag
      from raw_dataset rd
     ) rd;

逻辑很简单。看看前面的旗帜。然后在值变化的时候做一个累加max()

Here 是一个 db<>fiddle.

在每行更改值时附上最近的时间戳

Attach the most recent timestamp when value was changed to each row

sql

presto

user_id	flag	updated_at	recent_updated_at
123	1	101	101
123	0	102	102
123	1	103	103
123	1	104	103
123	1	105	103
124	0	101	101
124	0	102	101
124	0	110	101

user_id	flag	updated_at	recent_updated_at
123	1	101	101
123	0	102	102
123	1	103	103
123	1	104	103
123	1	105	103
124	0	101	101
124	0	102	101
124	0	110	101

user_id	flag	updated_at	recent_updated_at
123	1	101	101
123	0	102	102
123	1	103	103
123	1	104	103
123	1	105	103
124	0	101	101
124	0	102	101
124	0	110	101