I want a overview of used payment methods for the pas 6 month i.e. 200 orders: 100 creditcard, 70 paypal, 30 bank transfer
Is there a handy way to get this kind of information in php, mysql or ....
You did not define where the data should be retrieved/viewed: Should it be possible to generate a report for the admins in the backend or is a one time SQL query enough?
For the first: I've seen Mirasvit Advanced Reports has a lot of reports, and also a function to filter per payment time and limit the time period.
For the second: You can write a query that queries sales_flat_order and sales_flat_order_payment.
SELECT sales_flat_order_payment.method, COUNT(*) FROM sales_flat_order JOIN sales_flat_order_payment ON sales_flat_order_payment.parent_id = sales_flat_order.entity_id WHERE created_at > DATE_SUB(NOW(), INTERVAL 6 MONTH) GROUP BY sales_flat_order_payment.method