How to make Row_number() based on condition? - sql-server

Question

I have list of sample data. Using this I need new column which having sequence number. But condition of this sequence number is if consecutively InRange column value 1 then only it generate sequence number.In between if InRange value 0 then again sequence number start from 1 and so on.
Below query which I have created but not return expected result.
CREATE TABLE #Result (ID INT,Value INT,InRange BIT)
INSERT INTO #Result
SELECT 1 ,211,0
UNION SELECT 2 ,205,1
UNION SELECT 3 ,214,0
UNION SELECT 4 ,202,1
UNION SELECT 5 ,204,1
UNION SELECT 6 ,203,1
UNION SELECT 7 ,209,0
UNION SELECT 8 ,216,0
UNION SELECT 9 ,205,1
UNION SELECT 10 ,224,0
Query:
SELECT *
,CASE WHEN InRange=1 THEN ROW_NUMBER()OVER(Order by Id asc) ELSE 0 END AS ExpectedColumn
FROM #Result
Expected result.
ID Value InRange ExpectedColumn
1 211 0 0
2 205 1 1
3 214 0 0
4 202 1 1
5 204 1 2
6 203 1 3
7 209 0 0
8 216 0 0
9 205 1 1
10 224 0 0

Answer 1

This is a gaps and islands problem, with the islands being each group of records to which you want to assign its own row number sequence. One straightforward way to handle this uses the difference in row numbers method:
WITH cte1 AS (
SELECT *, ROW_NUMBER() OVER (ORDER BY ID) rn1
FROM #Result
WHERE InRange = 1
),
cte2 AS (
SELECT t1.*,
ROW_NUMBER() OVER (ORDER BY t1.ID) - t2.rn1 AS diff
FROM #Result t1
LEFT JOIN cte1 t2
ON t1.ID = t2.ID
)
SELECT ID, Value, InRange,
CASE WHEN InRange <> 0
THEN ROW_NUMBER() OVER (PARTITION BY diff ORDER BY ID)
ELSE 0 END AS ExpectedColumn
FROM cte2
ORDER BY ID;
Demo

Answer 2

with grouped_data as (
select
*,
count(case when InRange = 0 then 1 else null end) over(order by ID rows between unbounded preceding and current row) as group_number
from #Result
)
select
ID,
Value,
InRange,
row_number() over(partition by group_number order by ID) - 1 as expected_column
from grouped_data
order by ID;