Question

I’m writing some SQL for our lab, and I have it all done except for the fact that I need to count the DISTINCT number of samples that get returned. Here is the working code without COUNT() incorporated. It ties together three tables. When I use a COUNT() function, I get inaccurate results. Do I need to incorporate a subquery in SELECT?

SELECT
  batchid,
  s_sampleid, 
  requestid, 
  u_labinstance, 
  sdiworkitem.workitemid,
  workitemdesc
FROM s_sample INNER JOIN (sdiworkitem INNER JOIN workitem ON sdiworkitem.workitemid = workitem.workitemid)
ON s_sample.s_sampleid = sdiworkitem.keyid1
GROUP BY
  s_sampleid, 
  batchid, 
  requestid, 
  u_labinstance, 
  sdiworkitem.workitemid,
  workitemdesc

UPDATE (Working Query)

SELECT
  batchid,
  COUNT(DISTINCT s_sampleid),
  s_sampleid, 
  requestid, 
  u_labinstance, 
  sdiworkitem.workitemid,
  workitemdesc
FROM s_sample INNER JOIN (sdiworkitem INNER JOIN workitem ON sdiworkitem.workitemid = workitem.workitemid)
ON s_sample.s_sampleid = sdiworkitem.keyid1
GROUP BY
  batchid, 
  requestid, 
  u_labinstance, 
  sdiworkitem.workitemid,
  workitemdesc

Answer 1

First, take out s_sampleid from the GROUP BY

GROUP BY
  batchid, 
  requestid, 
  u_labinstance, 
  sdiworkitem.workitemid,
  workitemdesc

Then, try both of these

COUNT(DISTINCT s_sampleid)
COUNT(s_sampleid)

The GROUP BY on s_sampleid will always give “1” so fix that, then see which of these COUNTs is correct.

Edit:

If you need the actual s_sampleid and the count, then you need the OVER clause and remove the GROUP BY

 COUNT(DISTINCT s_sampleid) OVER (PARTITION BY batchid, 
  requestid, 
  u_labinstance, 
  sdiworkitem.workitemid,
  workitemdesc)

This should work… otherwise it’s a sub query

Otherwise, you should have mentioned you want the values and the count at the start