Date / Time calculation help

[Fisher]

I'm having trouble getting my head around this.
I have a database that collects stats of patients admitted to ICU.
I have a table PtDataTable (pk = PtID) with a one to many relationship with PtVisitTable (pk = VisitID, fk = PtID). The patient visit table has the fields AdmissionDate and AdmissionTime, and DischargeDate and DischargeTime.
I need to calculate if the patient is readmitted to ICU in less than or equal to 48hrs. In other words calculate the time elapsed between DischargedDate and DischargedTime in one record and the AdmissionDate and AdmissionTime for other records in the PtVisitTable for the same patient.
I'm not sure if I stated this clearly.
Any help is appreciated as always.

 

[wardster]

Hi - I found the following link a very usefull knowledge base for this type of datediff calculations

http://support.microsoft.com/?scid=kb;en-us;210604&spid=2509&sid=202

Regards - Ian

 

[Fisher]

I'm sorry for replying after such a long time. I couldn't back to it.
Anyhow, I'm still having problems with the date calculations between different records. The article referenced seems to discuss time calculations for each record.
I need to find the elapsed time from the discharge date and time of one record and the admission date and time of the next record for the same patient.