CREATE TABLE #temp(i int, flag bit NOT NULL)
INSERT INTO #temp VALUES(1, 1)
INSERT INTO #temp VALUES(2, 0)
INSERT INTO #temp VALUES(NULL, 0)

--returns 2 and NULL
SELECT i FROM #temp WHERE flag=0

--returns 1
SELECT i FROM #temp WHERE flag=1

--you would expect this to return 1, just like the query before, but it returns nothing!
SELECT i FROM #temp WHERE i not in (SELECT i FROM #temp WHERE flag=0)

--this corrected query returns 1, as it should
SELECT i FROM #temp WHERE i not in (SELECT i FROM #temp WHERE flag=0 AND i IS NOT NULL)

( Comments |Comment on this)

StartDelay := GetTickCount();

repeat
   Application.ProcessMessages;
until (abs((GetTickCount() - StartDelay))) >= PauseLength;

On Error Resume Next
Dim c As Collection
   'comment out to show the bug
   'Set c = New Collection
   'c.Add "Shit"
   'since c wasn't initialized, accessing it's property raises an error
   'you'd think that Resume Next will go to the line after End If, but...
   If c.Count > 0 Then
      MsgBox "Shit happened"
   End If

Dim Everything As Object

If Everything Is Nothing Then
   MsgBox "Everything Is Nothing"
End If

SELECT A.Field, B.Field, C.Field
FROM A LEFT JOIN B ON A.Key=B.Key
       LEFT JOIN C ON A.Key=C.Key

FROM (A LEFT JOIN B ON A.Key=B.Key)
       LEFT JOIN C ON A.Key=C.Key