Can I get an equivalent query for this Not in Query
You don't select those ids that are minimum in their systemno group so you select only those that have a lower id in their group:

SELECT id FROM dbo.SomeTable st1
WHERE EXISTS
  (
    SELECT *
    FROM dbo.SomeTable st2
    WHERE st1.SystemNo = st2.SystemNo AND st2.id &lt; st1.i
  )