Counting Consecutive Weeks based on separate numeric column - sql

Question

I'm working on a problem where the employees get a certain score each week. They will only have 1 score each week, being saved each Saturday. I want to count the number of consecutive weeks (working backwards from today) that they are above 50. If the previous week is not above 50 then they would have 0 consecutive weeks. If they've had a score above 50 each week for the past year, then they would have 52 consecutive weeks.
I've tried using the Row_Number() function to get this, but can't figure out how to incorporate the score as a factor in that.
This is an example of the data set:
EmpID Last Week Score
A 7/6/2019 60
A 6/29/2019 84
A 6/22/2019 21
B 7/6/2019 41
B 6/29/2019 92
C 7/6/2019 77
C 6/29/2019 55
C 6/22/2019 71
C 6/15/2019 63
This is what I've tried so far
SELECT
EmpID,
EOW,
SCORE,
ROW_NUMBER() OVER(PARTITION BY EMP ORDER BY EOW DESC) AS RN
FROM a
ORDER BY EmpID, EOW DESC
But that only gives me a row count of each employee. I need the count to stop when their score is below 50 as below:
EmpID Last Week Score RN
A 7/6/2019 60 1
A 6/29/2019 84 2
A 6/22/2019 21 -
B 7/6/2019 41 -
B 6/29/2019 92 -
C 7/6/2019 77 1
C 6/29/2019 55 2
C 6/22/2019 71 3
C 6/15/2019 63 4
I then need to get a single number of the consecutive weeks for each employee so that I can join the results to a larger query that pulls additional info about the employee. The scores are in a different table which is why I have to join it. The query should produce a result like:
EmpID Last Week Consecutive Week
A 7/6/2019 2
B 7/6/2019 0
C 7/6/2019 4
Does this make sense? Any help would be appreciated

Answer 1

I used conditional aggregation and running total.
The basic idea is:
If the number >= 50, the derived column will sum 0.
The consecutive zero(s) will stop at the first <50 value.
Then count the number of zeros.
I added the special case [group D]:
('D','7/6/2019' , 51 )
('D','6/29/2019' , 49)
('D','6/22/2019' ,52 )
There will be one single zero in this case.
If there is only one zero, I think the consecutive weeks should be zero instead of one.
I added [group D] into the test sample.
Try this:
SELECT B.EmpID,B.[Last Week], CASE WHEN B.TOTAL <= 1 THEN 0 ELSE B.TOTAL END AS RN
FROM (
SELECT A.EmpID, MAX(EOW) AS [Last Week], SUM(CASE WHEN A.COUNT1 = 0 THEN 1 ELSE 0 END) AS TOTAL
FROM
(
SELECT EMPID,EOW, Score
, SUM(CASE WHEN SCORE >= 50 THEN 0 ELSE 1 END) OVER (PARTITION BY EMPID ORDER BY EOW DESC) AS COUNT1
FROM TEST
GROUP BY EMPID,EOW,Score
)A
GROUP BY A.EmpID
)B
Test Result:
DB<>Fiddle