>>
>>select *, sum(uurfact) as fact, SUM(IIF(ureisk='Ja ',1,0)) as reisk from uren where umcode= '20002 ' group by umcode
>>

The TSQL version would look like this:

SELECT *,
SUM(CASE WHEN ureisk = 'Ja ' THEN 1 ELSE 0 END) as ...

HTH

-Mike