What is the percentage of payment methods of donations made in March 2013?
made in March 2013 refers to substr(donation_timestamp,1,7) = '2013-03'; percentage refers to DIVIDE(SUM(payment_method made in March 2013), SUM(payment_method))*100
SELECT payment_method , CAST(COUNT(donationid) AS REAL) * 100 / 51090 FROM donations WHERE donation_timestamp LIKE '2013-03%' GROUP BY payment_method