QUESTION:
On Magento CE 1.7.0.2 we already have custom filter columns added on the backend for Sales->Orders.
The SKU number was one of the custom filters we added however the problem was that it listed only the first SKU# per order when the client wanted to see ALL THE SKU#s on Sales Order view.
ANSWER:
I did research trying to figure this out and was about to post question here on StackOverflow when I found the following thread:
https://stackoverflow.com/a/11788680/1738977
^^ From that answer we implemented it almost exactly the same however:
Didn't need to add filter_skus function.
Slight modifications made for function callback_skus to add commas when more than one sku present.
Within the _prepareCollection() function added the sku column differently.
You may download app/code/local/Mage/Adminhtml/Block/Sales/Order/grid.php from: http://www.mediafire.com/?9znu9kdgq131y66
Notice that I have it in app/code/local/... If you don't have this folder currently you'll need to create it and the folders after it then upload grid.php
Please let me know if what I wrote is clear enough or if I need to improve it.
Best Regards,
George