[Solved] First 5 entries for a single user

Try this query:

SELECT cust_id, date
FROM (
  SELECT cust_id,
         date,
         row_number() OVER (partition by cust_id
                            ORDER BY date, id ) rn
  FROM Transaction
) as alias
WHERE rn <= 5
ORDER BY 1,2

demo: http://sqlfiddle.com/#!15/cfd2e/4