Distinct patients in time period

[Guest]

I have a table that contains patients who have had tests for a particular
organism and I need to count how many 'new' patients have been screened in a
particular time period. For example, John Smith could have 7 tests during
Jan, Feb, Mar and Apr. I only want him to be counted in January's figures -
if I run a query for March and April only I don't want him to be included.
The MIN of date reported would work without date parameters but with them it
gives me Mr Smith's first appearance in the time period specified, which
could be the 4th time he's been tested. I hope this makes sense - can anyone
give me a starter?!

 

[Guest]

Use the MIN of date reported would work without date parameters to give Mr
Smith's first appearance. Then a second query using the first as source to
see if the first is in the report time frame. If not then Mr Smith is not
included.