Increment column for streaks - sql

Question

How do I get the following result highlighted in yellow?
Essentially I want a calculated field which increments by 1 when VeganOption = 1 and is zero when VeganOption = 0
I have tried using the following query but using partition continues to increment after a zero. I'm a bit stuck on this one.
SELECT [UniqueId]
,[Meal]
,[VDate]
,[VeganOption]
, row_number() over (partition by [VeganOption] order by [UniqueId])
FROM [Control]
order by [UniqueId]
Table Data:
CREATE TABLE Control
([UniqueId] int, [Meal] varchar(10), [VDate] datetime, [VeganOption] int);
INSERT INTO Control ([UniqueId], [Meal], [VDate], [VeganOption])
VALUES
('1', 'Breakfast',' 2018-08-01 00:00:00', 1),
('2', 'Lunch',' 2018-08-01 00:00:00', 1),
('3', 'Dinner',' 2018-08-01 00:00:00', 1),
('4', 'Breakfast',' 2018-08-02 00:00:00', 1),
('5', 'Lunch',' 2018-08-02 00:00:00', 0),
('6', 'Dinner',' 2018-08-02 00:00:00', 0),
('7', 'Breakfast',' 2018-08-03 00:00:00', 1),
('8', 'Lunch',' 2018-08-03 00:00:00', 1),
('9', 'Dinner',' 2018-08-03 00:00:00', 1),
('10', 'Breakfast',' 2018-08-04 00:00:00', 0),
('11', 'Lunch',' 2018-08-04 00:00:00', 1),
('12', 'Dinner',' 2018-08-04 00:00:00', 1)
;
This is for SQL Server 2016+

Answer 1

You could create subgroups using SUM and then ROW_NUMBER:
WITH cte AS (
SELECT [UniqueId]
,[Meal]
,[VDate]
,[VeganOption]
,sum(CASE WHEN VeganOption = 1 THEN 0 ELSE 1 END)
over (order by [UniqueId]) AS grp --switching 0 <-> 1
FROM [Control]
)
SELECT *,CASE WHEN VeganOption =0 THEN 0
ELSE ROW_NUMBER() OVER(PARTITION BY veganOption, grp ORDER BY [UniqueId])
END AS VeganStreak -- main group and calculated subgroup
FROM cte
order by [UniqueId];
Rextester Demo

Answer 2

This is a variant on gaps-and-islands.
I like to define streaks using the difference of row numbers. This looks like
select c.*,
(case when veganoption = 1
then row_number() over (partition by veganoption, seqnum - seqnum_v order by uniqueid)
else 0
end) as veganstreak
from (select c.*,
row_number() over (partition by veganoption order by uniqueid) as seqnum_v,
row_number() over (order by uniqueid) as seqnum
from c
) c;
Why this works is a bit hard to explain. But, if you look at the results of the subquery, you'll see how the difference of row numbers defines the streaks you want to identify. The rest is just applying row_number() to enumerate the meals.
Here is a Rextester.

Answer 3

One method is to use a CTE to define your groupings, and then do a further ROW_NUMBER() on those, resulting in:
WITH Grps AS(
SELECT *,
ROW_NUMBER() OVER (ORDER BY UniqueID ASC) -
ROW_NUMBER() OVER (PARTITION BY VeganOption ORDER BY UniqueID ASC) AS Grp
FROM Control)
SELECT *,
CASE VeganOption WHEN 0 THEN 0 ELSE ROW_NUMBER() OVER (PARTITION BY Grp ORDER BY UniqueID ASC) END
FROM Grps
ORDER BY UniqueId;