Question

I have three tables…

Given the following tables I would like to know how to write a query to return all the book sorted by month and with a
average price per month table (that would be something like SUM(invoices.total)/COUNT(invoices.total).
I have a date field which has a format of 2010-03-30, and I would like to get the months out of if…so I can sort the sum
by month. I’m using PHP and MySQL.
Thank you in advance!

books

-call_started

books_chapters

-id

invoices

-id

-invoice_type

-chapters_id

-total

Answer 1

I can not construct the full query from the schema in your question but you can group the results – GROUP BY(CONCAT(YEAR(date_field), MONTH(date_field))

If you elaborate or comment, I will improve my answer.