rownumber_mysql2.sql

SET @rank = 0; 

SELECT 
  company_name, 
  sale_date, 
  total_amount, 
  day_rank 
FROM ( 
  SELECT 
    company_name, 
    sale_date, 
    total_amount, 
    @rank := IF( @comp_id = company_id, @rank + 1, 1) AS day_rank, 
    @comp_id := company_id 
  FROM 
    company_sales 
  ORDER BY 
    company_id, total_amount DESC) rankings 
ORDER BY 
  company_name, day_rank