Report on return customers

[DrByte]

This may look odd, but it should work as-is, on MySQL 5.0 or greater:

SET @custcount=0;
SELECT (@custcount:=count(*)) as custcount 
FROM customers;
SELECT numorders, count(numorders) as numcusts, @custcount as totalcustomers, count(numorders)/@custcount as percent
FROM (SELECT count(orders_id) AS numorders 
FROM  orders GROUP BY customers_id) o
GROUP BY (o.numorders) ORDER BY numorders DESC;

If you're using custom table prefixes, you'll need to add your prefix to the two highlighted tablenames.