Query to find three instances the same in one column, but must be have three different results in another column - sql

Question

I have a table like the following:
InspectDate | Serial Number | Reference | Error | PartNumber
I need to find the data of errors that occurred in the last 10 days. I can get that, but then I need to find only those problems that occurred on the same reference, but only if they happen to be on three or more different serial numbers.
Please let me know if I need to provide any more info. I have tried using count and filtering by those with more than 3, but that only shows me any one serial number that has more than three errors on that reference.
Sample Data:
InspectDate SerialNumber Reference Error PartNumber
Oct 12 2021 1:58PM 50012 A21 1 PL2-001
Oct 12 2021 3:22PM 50013 A21 1 PL2-001
Oct 12 2021 5:59PM 50062 A21 1 PL2-001
Oct 18 2021 11:24AM 50071 A21 1 PL2-001
Oct 18 2021 12:20PM 50071 A21 2 PL2-001
Oct 18 2021 12:36PM 50071 A21 3 PL2-001
Oct 12 2021 5:59PM 50055 B44 5 AL1-440
Oct 18 2021 11:19AM 50062 B72 1 AL1-660
Oct 18 2021 11:22AM 50071 B72 2 AL1-660
Oct 12 2021 5:39PM 50047 B83 5 AL1-550
Oct 12 2021 3:03PM 50013 V310 2 PL3-010
Oct 18 2021 12:00PM 50071 V310 2 PL3-010
Oct 18 2021 12:37PM 50098 V310 4 PL3-010
Expected Results:
InspectDate SerialNumber Reference Error PartNumber
Oct 12 2021 1:58PM 50012 A21 1 PL2-001
Oct 12 2021 3:22PM 50013 A21 1 PL2-001
Oct 12 2021 5:59PM 50062 A21 1 PL2-001
Oct 18 2021 11:24AM 50071 A21 1 PL2-001
Oct 12 2021 3:03PM 50013 V310 2 PL3-010
Oct 18 2021 12:00PM 50071 V310 2 PL3-010
Oct 18 2021 12:37PM 50098 V310 4 PL3-010
Tempted Code:
Select (all columns), COUNT() AS Instances From (Table)
Where InspectDate >= DATEADD(day, -10, GETDATE())
GROUP BY (all columns)
HAVING COUNT() >= 3
Order by CAST (inspectdate as datetime) DESC

Answer 1

What you need here is a windowed COUNT(DISTINCT. Unfortuantely, SQL Server does not allow COUNT(DISTINCT as a window function.
But we can simulate it using DENSE_RANK and MAX, both as window functions
WITH Ranked AS (
SELECT *,
rn = DENSE_RANK() OVER (PARTITION BY Reference ORDER BY SerialNumber)
FROM [Table]
WHERE InspectDate >= DATEADD(day, -10, GETDATE())
),
DistinctCount AS (
SELECT *,
maxrn = MAX(rn) OVER (PARTITION BY Reference)
FROM Ranked
)
SELECT *
FROM DistinctCount
WHERE maxrn >= 3;