表包含文件名和大小...需要查询以返回每种文件类型的计数和每种类型的总和大小

I have a table that has a file name column and a file size column. I'd like to generate a report that counts how many of each file type there is and how much space the sum of each file type is consuming. Using substring_index I can return just the file extension in one column and the file size in the next, then I believe I can use COUNT(*) and SUM and GROUP BY in some proper fashion to get the results... but I can't seem to sort it out...I have a table that has a file name column and