Query: Find the earliest date with a null entry which still works with no null entries - sql

Question

I am building a query that displays the next due date for users. The number of dates stays the same, but the due date will change, depending on how many records have a comment from the user.
SELECT tbl_Description.Sample,
tbl_Description.User,
Min(tbl_Data.TestDate) As DueDate
FROM tbl_Description
INNER
JOIN tbl_Data
ON tbl_Description.DescriptionID = tbl_Data.DateID
WHERE tbl_Data.Comment IS NULL
GROUP
BY tbl_Description.Sample,
tbl_Description.User;
However, when every record from tbl_Data has a comment, the query returns empty records. This may happen because the WHERE and IS NULL statement returns nothing if every record exists. Preferably, I would still like the null record to appear with something in the [DueDate] field, such as a blank or “Complete” comment.
tbl_Description
Sample User
1 Betty
tbl_Data (v1)
Date Comments
05/01/2018 Orange
05/08/2018 Orange-Brown
05/15/2018
05/22/2018
Query Output
Sample User DueDate
1 Betty 05/15/2018
tbl_Data (v2)
Date Comments
05/01/2018 Orange
05/08/2018 Orange-Brown
05/15/2018 Brown
05/22/2018 Brown-Black
Query Output (Query returns nothing at the moment)
Sample User DueDate
1 Betty Complete
Any help would be appreciated!

Answer 1

Now knowing that we also can group by DescriptionID, I suggest to query the minimum TestDate for records from tbl_Data without a Comment separately and (outer) join the result to the table tbl_Description. This way, each Description is contained in the result, and when all Dates for a Description have a Comment, the DueDate will appear blank:
SELECT tbl_Description.Sample, tbl_Description.User, Uncommented.DueDate
FROM tbl_Description
LEFT JOIN (
SELECT tbl_Data.DateID, Min(tbl_Data.TestDate) AS DueDate
FROM tbl_Data
WHERE (((tbl_Data.Comment) Is Null))
GROUP BY tbl_Data.DateID
) AS Uncommented ON tbl_Description.DescriptionID = Uncommented.DateID;