Row_number skip values - sql

Question

I have a table like this:
The idea were to count only when I have "Include" at column include_appt, when it finds NULL, it should skip set is as "NULL" or "0" and on next found "Include" back to counting where it stopped.
The screenshot above I was almost able to do it but unfortunately the count didn't reset on next value.
PS: I can't use over partition because I have to keep the order by id ASC

Answer 1

I suggest using the DENSE_RANK() with the columns you have hidden (--*,):
SELECT
row_num AS id,
include_appt,
CASE WHEN include_appt is not null
THEN ROW_NUMBER() OVER(ORDER BY (SELECT 0))
+ 1
- DENSE_RANK() OVER(
PARTITION BY /*some hidden columns*/
ORDER BY/*some hidden columns*/)
ELSE NULL
END AS row_num2
FROM C
ORDER BY row_num
Then the result will be:
enter image description here

Answer 2

If you are trying to prevent row numbers being added for NULL/0 values, why not try a query like this instead?
SELECT
row_num AS id,
include_appt,
ROW_NUMBER() OVER
(
ORDER BY (SELECT 0)
) AS row_num2
FROM C
WHERE ISNULL(C.include_appt, 0) <> 0
ORDER BY row_num
I would recommend reconsidering the column names/aliases you want to have displayed in your final result to avoid confusion, but the above should effectively do what you are wanting.

Answer 3

You need a PARTITION BY clause
SELECT
row_num AS id,
include_appt,
CASE WHEN include_appt IS NULL
THEN 0
ELSE
ROW_NUMBER() OVER (PARTITION BY include_appt ORDER BY (SELECT 0))
END AS row_num2
FROM C
ORDER BY row_num

Answer 4

SELECT id, include_appt,
CASE WHEN include_appt IS NULL THEN 0
ELSE ROW_NUMBER() OVER (PARTITION BY include_appt ORDER BY id ASC)
END AS row_num
FROM #1 ORDER BY id asc

Answer 5

This can be easily done with a partition by include_appt as in another answer below, yet after playing around with the query plans I've decided that it is still worthwhile to consider this slightly different approach which might offer a performance boost. I believe the benefit is gained by being able to use the clustered index without involving a sort on the flag column:
select id, flag,
case when flag is not null
then row_number() over (order by id)
- count(case when flag is null then 1 end) over (order by id)
else 0 end /* count up the skips */ as new_rn
from T
order by id
Examples (including a "reset" behavior): https://dbfiddle.uk/?rdbms=sqlserver_2014&fiddle=c9f4c187c494d2a402e43a3b24924581
Performance comparison:
https://dbfiddle.uk/?rdbms=sqlserver_2014&fiddle=719f7bd26135ab498d11c786f1b1b28b