Kannst du mal gucken, ob es so richtig ist?
..WHERE (
(CONVERT(char(8), Von, 108) BETWEEN '00:00:00' AND '23:59:59'
AND CONVERT(char(8), Bis, 108) BETWEEN '00:00:00' AND '23:59:59')
OR
(CONVERT(char(8), Von, 108) BETWEEN '00:00:00' AND '23:59:59'
AND Bis Is Null)
AND
(
(Von BETWEEN '14.12.2005 00:00:00' AND '22.12.2005 23:59:59' AND Bis BETWEEN '14.12.2005' AND '22.12.2005')
OR
(Von BETWEEN '14.12.2005' AND '22.12.2005' AND Bis Is Null)))
Danke!