Aggregate functions in SQL, add 1 condition

[Lifeseeker]

Hi,

I'm struggling with this aggregate function in SQL, and am wondering if someone could point me in the right direction.

The code is as follows:


SELECT Format(Sum(IIf(DateDiff("h",[start date],[abc_time])<=10,1,0))/Count([abc_test_done]),"Percent") AS PercentOfInterest
FROM tbl_record
WHERE (((tbl_record.abc_Test_Done)="yes"));

I simply want to do the exact same calculation for 2 different hospitals, but where would I add that location condition?

Shall I put in the WHERE clause? But then wouldn't I have to count the location as well for the numerator and denominator?

Please any comment/feedback is much appreciated.