Calculating count over partition

Question

I have a table that looks like this:

I want to make a new column which specifies count of mileage for each car. The output should look like this:

Basically, the new column is counting the occurrences for the mileage for EACH car type.

Here's what I'm using in my SQlite query:

 SELECT *, COUNT(Mileage) OVER (PARTITION BY Mileage ORDER BY Car) Count_mileage FROM car_table GROUP BY Car, Mileage

However, it does not give the accurate answer, as it takes count of mileage without partitioning into cars.

Can anybody help.

Answer 1

The partition should be over Car also and there is no need for the ORDER BY clause:

SELECT *,
       COUNT(*) OVER (PARTITION BY Car, Mileage) Count_mileage
FROM car_table

Also the GROUP BY clause is not needed.