sql copying duplicates - sql

Question

I'm trying to fill 'Col4' null values with the values above using 'Col1' and 'Col3'. Here is a brief explanation of the columns:
Col1 - User Entry date
Col2 - Calendar date
Col3 - Difference between the dates in Col1
Col4 - Entry amount
What the data currently looks like:
| Col1 | Col2 | Col3 | Col4
| 2016-01-01 | 2016-01-01 | 3 | $10
| null | 2016-01-02 | null | null
| null | 2016-01-03 | null | null
| 2016-01-04 | 2016-01-04 | 1 | $2
| 2016-01-05 | 2016-01-05 | 2 | $7
| null | 2016-01-06 | null | null
| 2016-01-07 | 2016-01-07 | 3 | $5
| null | 2016-01-08 | null | null
| null | 2016-01-09 | null | null
Expected Results:
| Col1 | Col2 | Col3 | Col4
| 2016-01-01 | 2016-01-01 | 3 | $10
| null | 2016-01-02 | null | $10
| null | 2016-01-03 | null | $10
| 2016-01-04 | 2016-01-04 | 1 | $2
| 2016-01-05 | 2016-01-05 | 2 | $7
| null | 2016-01-06 | null | $7
| 2016-01-07 | 2016-01-07 | 3 | $5
| null | 2016-01-08 | null | $5
| null | 2016-01-09 | null | $5
The formula works by counting the number in Col3 and then copying the corresponding amount in Col4 to the rows below. Col3 defines how many rows below (including its own row).
I'm currently using Sybase. I don't have any ideas on how I can do this. Any help would be appreciated thanks.
Note: this is a sample of data and the dates go from 2000 - 2016

Answer 1

In SQL Server By given sample data we can achieve the above result Set by using CTE
Sample Data :
declarE #Table1 TABLE
(Col1 varchar(10), Col2 varchar(10), Col3 varchar(4), Col4 varchar(4))
;
INSERT INTO #Table1
(Col1, Col2, Col3, Col4)
VALUES
('2016-01-01', '2016-01-01', '3', '$10'),
(NULL, '2016-01-02', NULL, NULL),
(NULL, '2016-01-03', NULL, NULL),
('2016-01-04', '2016-01-04', '1', '$2'),
('2016-01-05', '2016-01-05', '2', '$7'),
(NULL, '2016-01-06', NULL, NULL),
('2016-01-07', '2016-01-07', '3', '$5'),
(NULL, '2016-01-08', NULL, NULL),
(NULL, '2016-01-09', NULL, NULL)
;
Script :
WITH cte
AS (SELECT T1.Col1,
T1.Col2,
T1.Col3,
Col4 = COALESCE(T1.Col4, (SELECT TOP 1 Col4
FROM #Table1 T2
WHERE T2.Col2 < T1.Col2
AND Col4 IS NOT NULL
ORDER BY Col2 DESC))
FROM #Table1 T1)
UPDATE T
SET
T.Col4 = C.Col4
FROM #Table1 T
INNER JOIN cte C
ON T.col2 = C.col2
WHERE T.col1 IS NULL
OR T.col2 IS NULL
OR T.col3 IS NULL
Select * from #Table1