Question

My query works fine; however, I need to join another dataset to my query, and I expect that the count(f.*) will break.

Here’s the query I start with:

SELECT
       MIN(received_date) AS FirstVisit
     , patient_id         AS PatientID
INTO #LookupTable
FROM F_ACCESSION_DAILY

SELECT 
       f.doctor           AS Doctor
     , COUNT(f.*)         AS CountNewPatients
     , MONTH(firstvisit)  AS Month
     , YEAR(firstvisit)   AS Year
FROM F_ACCESSION_DAILY f 
INNER JOIN #LookupTable l ON f.received_date = l.FirstVisit 
                         AND f.patient_id = l.PatientID
GROUP BY f.doctor
       , MONTH(firstvisit)
       , YEAR(firstvisit)

DROP TABLE #LookupTable

I would like to Join the above query on another table.

The question is *will my count(f.*) stay the same or will it change because I’ve added a new dataset?*

**How do I make sure that the count(f.*) will remain the same?

Thank you so much for your guidance.

Answer 1

will my count(f.*) stay the same or will it change because I’ve added a new dataset?*

COUNT(*) counts rows. If you join another table and the number of rows increases, the result of COUNT(*) will increase.

How do I make sure that the count(f.*) will remain the same?

Use COUNT (DISTINCT f.Id).