Select all rows after first x rows containing NULLs

I have table src. In this table, each Product-Country combination might contain NULL in the Country column for the first x rows.

How can I SELECT rows for each Product-Country combination, only rows after the first x rows that contain NULL in the Country column? It's important to also SELECT any latter rows, even if they do contain NULL in the Country column, as long as there was at least one row with a true value, prior to it.

Expected Output

For example.

• For product A, I would like to SELECT rows with ID 3 and 4, but not ID 1 and 2.

• For Product B, I would like to SELECT rows with ID 6 and 7, but not ID 5.

ID
Product
Country
Timestamp

3
A
AT
2022-01-23 14:29:06.830

4
A
NULL
2022-01-24 14:29:06.830

6
B
CH
2022-01-23 14:29:06.830

7
B
NULL
2022-01-24 14:29:06.830

Sample Table and Data

create table dbo.src
(
    ID int not null
    ,Product varchar(2) not null
    ,Country varchar(2) null
    ,[Timestamp] datetime not null
)

insert into dbo.src
    (ID,Product, Country, [Timestamp])
values
    (1,'A',NULL,'2022-01-21 14:29:06.830')
    ,(2,'A',NULL,'2022-01-22 14:29:06.830')
    ,(3,'A','AT','2022-01-23 14:29:06.830')
    ,(4,'A',NULL,'2022-01-24 14:29:06.830')
    ,(5,'B',NULL,'2022-01-22 14:29:06.830')
    ,(6,'B','CH','2022-01-23 14:29:06.830')
    ,(7,'B',NULL,'2022-01-24 14:29:06.830')

Something like this should work. Use a cte to find the first ID for each product that is not null, then join back to the original table.

;WITH cMinProductId AS (
    SELECT Product, MIN(ID) MinID
    FROM dbo.src
    WHERE Country IS NOT NULL
    GROUP BY Product
)
SELECT s.*
FROM dbo.src AS s
INNER JOIN cMinProductId AS mp
    ON s.Product = mp.Product
WHERE s.ID >= mp.MinID

ID
Product
Country
Timestamp

3
A
AT
2022-01-23 14:29:06.830

4
A
NULL
2022-01-24 14:29:06.830

6
B
CH
2022-01-23 14:29:06.830

7
B
NULL
2022-01-24 14:29:06.830

Fiddle

StackExchange Database Administrators Q#306913, answer score: 5