Question

this seems simple but I cannot figure out how to do it or the proper description to correcltly google it 🙁

Briefly, have a table with:

PatientID | Date | Feature_of_Interest...

I’m wanting to plot some results for patients with multiple visits, when they have the feature of interest. No problem filtering out by feature of interest, but then I only want my resulting query to contain patients who have multiple entries.

SELECT PatientID,Date,...
    FROM myTable
    WHERE Feature_Of_Interest is present
    AND (Filter out PatientID's that only appear once)

So – just not sure how to approach this. I tried doing:

WITH X AS (Above SELECT, Count(*),...,Group by PatientID)

Then re-running query, but it did not work. I can post that all out if needed, but am getting the impression I am approaching this completely backward, so will defer for now.

Using SQL Server 2008.

Answer 1

You’ll want to join a subquery

JOIN (
    SELECT 
        PatientID
    FROM myTable 
    WHERE Feature_Of_Interest is present 
    GROUP BY PatientID
    HAVING COUNT(*) > 1
) s ON myTable.PatientID = s.PatientID