Daily status using prior value as backfill - sql

Question

This is the input table (tbl_statuslog):
User_id
isactive
date
1
1
1 Feb 2021
2
1
1 Feb 2021
3
1
2 Feb 2021
2
0
5 Feb 2021
4
1
10 Feb 2021
4
0
10 Feb 2021
3
0
12 Feb 2021
create table tbl_statuslog
(
[user_id] int,
[isactive] bit,
[date] datetime
);
insert into tbl_statuslog (user_id, isactive, date) values
(1, 1, ' 1 Feb 2021'),
(2, 1, ' 1 Feb 2021'),
(3, 1, ' 2 Feb 2021'),
(2, 0, ' 5 Feb 2021'),
(4, 1, '10 Feb 2021'),
(4, 0, '10 Feb 2021'),
(3, 0, '12 Feb 2021');
I want to return output, given today is 16 Feb:
User_id
isactive
date
1
1
1 Feb 2021
.
.
.
1
1
16 Feb 2021
2
1
1 Feb 2021
.
.
2
1
4 Feb 2021
2
0
5 Feb 2021
.
.
2
0
16 Feb 2021
3
1
2 Feb 2021
.
.
3
1
11 Feb 2021
3
0
12 Feb 2021
.
.
3
0
16 Feb 2021
4
0
10 Feb 2021
.
.
4
0
16 Feb 2021
I have used following SQL to get the list of all dates.
DECLARE #StartDateTime DATETIME
DECLARE #EndDateTime DATETIME
SET #StartDateTime = '2021-02-01'
SET #EndDateTime = GETDATE();
WITH DateRange(DateData) AS
(
SELECT #StartDateTime as Date
UNION ALL
SELECT DATEADD(d,1,DateData)
FROM DateRange
WHERE DateData < #EndDateTime
)
SELECT DateData
FROM DateRange
OPTION (MAXRECURSION 0)
GO
Now I am thinking of doing a left join of this table with tbl_statuslog table. Thus I have a date irrespective of whether date exists in tbl_statuslog or not.
Then I want to backfill the isactive value for the date and user_id based on the previous value.
Can I use window function- example partition by user_id, order by date to achieve the result?
I'm blocked here because when evaluating the isactive value for a date and userid, how can I get access to prior 1 day value, or value of 2 days prior (and so on) when the previous day doesn't have value?

Answer 1

This answers the original version of the question.
I would suggest using recursion but only for each row:
with ts as (
select ts.*,
lead(date) over (partition by user_id order by date) as next_date
from tbl_statuslog ts
),
cte as (
select user_id, date, isactive,
coalesce(dateadd(day, -1, next_date), convert(date, getdate())) as end_date
from ts
union all
select user_id, dateadd(day, 1, date), isactive, end_date
from cte
where date < end_date
)
select user_id, date, isactive
from cte;
Here is a db<>fiddle.