SQL i forbindelse med udregninger

What do you want to see exactly ion the New field?
Have you tried drawing your problem on a piece of paper just to see how many possibilities there are. Draw two vertical lines representing the periods you enter in the form. Then plot in other periods representing those that COULD come from your table. You will have at least 6 possibilities. Some where the period is between the forms start and end, some overlapping both the start and end. Others overlapping either the start or the end. And also those not overlapping at all.

So is it the tables start date, or the end date?
you are interested in. And in relation to the forms start or end date?

Hope you can see what the problem is.

Jeg er enig med Terry i, at der er 6 muligheder, men de kan nu forholdsvis let løses ved at finde maksimum for starttider og minimum for sluttider.

SELECT Tabel.Start1, Tabel.Slut1, Tabel.Start2, Tabel.Slut2, IIf([Start1]>[Start2],[Start1],[Start2]) AS Start3, IIf([Slut1]<[Slut2],[Slut1],[Slut2]) AS Slut3, IIf([Slut3]>=[Start3],DateDiff(\"d\",[Start3],[Slut3]),\"Intet overlap\") AS NDage
FROM Tabel;

I denne SQL-sætning har jeg antaget at begge tidsperioder (Start1-Slut1 og Start2-Slut2) er indeholdt i tabellen, men hvis nogle kommer fra en formular kan man i stedet skrive Forms!formularnavn!feltnavn &#8211; f.eks. Forms!DatoFormular!Start2

mvh/Jens-Peter

Tak for det begge to.
Jeg fik løst mit problem ud fra dit svar Jens. omend jeg lavede en funktion i VB til at løses det. Ikke helt sql. men det går indtil videre !.