I am trying to update a table using the following query
update at_product A join
(
SELECT atbillfields.billeditemguid,count(*) AS numberOfPeopleBought
,s
Have a look at:
http://justalittlebrain.wordpress.com/2010/09/15/you-are-using-safe-update-mode-and-you-tried-to-update-a-table-without-a-where-that-uses-a-key-column/
If you want to update without a where key you must execute
SET SQL_SAFE_UPDATES=0;
right before your query.
Another option is to rewrite your query o include a key.