Filling null row values with last non-null values - SQL table - sql-server

Question

I'm struggling with the following problem. Consider the example table posted below. What I need to do is to update the table, specifically the NULL values on each row with the "last" non-NULL values. For example, the NULL values on rows 3 and 4 should be updated with the values of row 2 of the same column, that is
2 007585102 2001 03 31 2001 04 12 2 154980 6300 154980 6300
3 007585102 2001 03 31 2001 04 19 2 154980 6300 154980 6300
4 007585102 2001 03 31 2001 04 26 2 154980 6300 154980 6300
and NULL values on rows 9 to 15 updated with the values of row 8 and so on.
I honestly have no idea how to do this and I will greatly appreciate any help. Thanks in advance.
Sorry about the extremely poor formatting of the table but I can't post anything but plain text.
EXAMPLE TABLE
1 007585102 2001 03 31 2001 04 05 2 543660 22100 543660 22100
2 007585102 2001 03 31 2001 04 12 2 154980 6300 154980 6300
3 007585102 NULL 2001 04 19 NULL NULL NULL NULL NULL
4 007585102 NULL 2001 04 26 NULL NULL NULL NULL NULL
5 007585102 2001 03 31 2001 05 03 2 2726664 110840 2726664 110840
6 007585102 2001 03 31 2001 05 10 2 836400 34000 836400 34000
7 007585102 2001 03 31 2001 05 17 2 534804 21740 7634364 310340
8 007585102 2001 03 31 2001 05 24 2 4920 200 4920 200
9 007585102 NULL 2001 05 31 NULL NULL NULL NULL NULL
10 007585102 NULL 2001 06 07 NULL NULL NULL NULL NULL
11 007585102 NULL 2001 06 14 NULL NULL NULL NULL NULL
12 007585102 NULL 2001 06 21 NULL NULL NULL NULL NULL
13 007585102 NULL 2001 06 28 NULL NULL NULL NULL NULL
14 007585102 NULL 2001 07 05 NULL NULL NULL NULL NULL
15 007585102 NULL 2001 07 12 NULL NULL NULL NULL NULL
16 007585102 2001 06 30 2001 07 19 2 2693301 118300 2693301 118300
17 007585102 2001 06 30 2001 07 26 2 232220 10200 NULL NULL

Answer 1

I'm not very proud of my answer, but at least it works. Find more elegant way on your own. I'd suggest recursive cte.
drop table #temp
GO
select
*
into #temp
from (
select 1 as id, '2001 03 31' as dat union all
select 2, '2001 03 31' union all
select 3, null union all
select 4, null union all
select 5, '2001 03 31' union all
select 6, '2001 03 31' union all
select 7, '2001 03 31' union all
select 8, '2001 03 31' union all
select 9, null union all
select 10, null union all
select 11, null union all
select 12, null union all
select 13, null union all
select 14, null union all
select 15, null union all
select 16, '2001 06 30' union all
select 17, '2001 06 30'
) x
update t
set
t.dat = t2.dat
from #temp t
join (
select
t1.id, max(t2.id) as maxid
from #temp t1
join #temp t2
on t1.id>t2.id
and t2.dat is not null
and t1.dat is null
group by
t1.id
) x
on t.id=x.id
join #temp t2
on t2.id=x.maxid
select * from #temp

Answer 2

I have explained this in details here:
https://koukia.ca/common-sql-problems-filling-null-values-with-preceding-non-null-values-ad538c9e62a6#.k0dxirgwu
here is the TSQL you need,
SELECT *
INTO #Temp
FROM ImportedSales;
;With CTE
As
(
SELECT ProductName
, Id
, COUNT(ProductName) OVER(ORDER BY Id ROWS UNBOUNDED PRECEDING) As MyGroup
FROM #Temp
),
GetProduct
AS
(
SELECT [ProductName]
, First_Value(ProductName) OVER(PARTITION BY MyGroup ORDER BY Id ROWS UNBOUNDED PRECEDING) As UpdatedProductName
FROM CTE
)
UPDATE GetProduct
Set ProductName = UpdatedProductName;
SELECT *
FROM #TemP;

Answer 3

In redshift, and I think other sql flavors, you can combine nvl() and lag functions, being sure to use the ignore nulls option when using lag().
I adapted this from https://blog.jooq.org/2015/12/17/how-to-fill-sparse-data-with-the-previous-non-empty-value-in-sql/ .
I'm going to the call the second date field in your example "date_field" since I didn't see a column header.
Let's assume you have a column called "row_number" on which you can correctly order your values.
Then the example using your above data would be like
select nvl(date_field,lag(date_field,1)) ignore nulls over ([partition by whatever] order by rownumber).
This should grab the nearest non-null value above in the column (which is ordered by whatever columns you specified), and replace the nulls until it hits a non-null value.
Ignore nulls is the key b/c otherwise you'll just grab the first non-null, then the next null, so that you only replace one row.
HTH.