How to populate missing date row with next date row in sql server?

Question

  date  value       
01-01-2020  2       
04-01-2020  3   
05-01-2020  5       
06-01-2020  7       
05-01-2020  9       

I want output:

date    value
01-01-2020  2
02-01-2020  3
03-01-2020  3
04-01-2020  3
05-01-2020  5
06-01-2020  7
07-01-2020  9
08-01-2020  9
09-01-2020  9
10-01-2020  9

WITH cte1 AS 
(
    SELECT *, 
      lead(date) OVER (ORDER BY date) AS NextDate FROM Screen1
) 
SELECT
  c.Date,
  t.value
FROM Calender1 c 
JOIN cte1 t ON c.Date 
  BETWEEN t.date AND ISNULL(DATEADD(day, -1, t.NextDate), t.date)

I have tried this but its duplicating the previous date value.In this query i have used a calender table and joined that table with main table which has missing dates.

Answer 1

First you need to have calendar table. Then you can find the next available value using CROSS APPLY and fill that value.

declare @table table(dateval date, val int)

insert into @table
values 
('2020-01-01',  2),
('2020-01-04',  3 ),  
('2020-01-05',  5 ),      
('2020-01-06',  7 ),      
('2020-01-10',  9)

DECLARE @StartDate DATE = '2020-01-01'
DECLARE @EndDate DATE = '2020-01-31'

;WITH Cal(n) AS
(
SELECT 0 UNION ALL SELECT n + 1 FROM Cal
WHERE n < DATEDIFF(DAY, @StartDate, @EndDate)
),
FnlDt(d) AS
(
SELECT DATEADD(DAY, n, @StartDate) FROM Cal
)


SELECT f.d, t.val
FROM FnlDt as f
CROSS APPLY
(select top 1 val from 
@table as t
where t.dateval >= f.d
order by t.dateval) as t(val)

d	val
2020-01-01	2
2020-01-02	3
2020-01-03	3
2020-01-04	3
2020-01-05	5
2020-01-06	7
2020-01-07	9
2020-01-08	9
2020-01-09	9
2020-01-10	9