Question

Can anyone please point out what is wrong with the following SQL statement:

SELECT DiaryType 
FROM tblDiaryTypes 
WHERE DiaryType NOT IN (SELECT NextDiary 
                        FROM tblActionLinks 
                        WHERE HistoryType = 'Info Chased');

Now the nested SELECT statement currently returns NULL because there are initially no entries in tblActionLinks, and I am wondering if that is the issue.

The outer SELECT statement if executed on its own does return all the Diary Types from tblDiaryTypes as expected. But when I add the nested SELECT statement to exclusde certain values, then the overall SQL statement returns empty!

Does this have something to do withthe fact that tblActionLinks is currently empty? If so, how can I amend my SQL statement to handle that possibility.

Answer 1

For SQL SERVER (you didn’t specified sql engine) try with:

SELECT ISNULL(NextDiary, 0)  ...

When no rows found all value is null then it will return 0