SQL average Percentage by group

Question

I have table1 with some sample record (would have more than 100 records)

lastname    courtesy    
Lane          3  
Lane          4  
Lane          5  
Lane         12   
Santana       4  
Santana       5  

My query to get the ave percent group by lastname and did not group by lastname
you can see Lane and Santana still not group.
Please correct the query. Thank you.

SELECT
  lastname,
  courtesy,
  percentage = AVG(courtesy) * 100 / SUM(AVG(courtesy)) OVER (PARTITION BY lastname)
FROM echo
GROUP BY
  lastname, courtesy

the results

lastname    courtesy    percentage
Lane         3           12
Lane         4           16
Lane         5           20
Lane         12          50
Santana      4           44
Santana      5           55

the results look like this

lastname    percentage
Lane         16        (4/24)
Satana       22        (2/9)

count (lastname) / sum (courtesy)  group by lastname

Answer 1

I think this is the logic that you want:

SELECT lastname,
       SUM(SUM(courtesy)) OVER (ORDER BY lastname),
       COUNT(*) * 1.0 / SUM(courtesy)
FROM echo
GROUP BY lastname;