Oracle GROUP BY question
Round to the beginning of the month:

SELECT     trunc(EntryDate,'MM'), COUNT(OrderNo)
FROM       Orders
GROUP BY   trunc(EntryDate,'MM');


In oracle 8i the results are sorted because of the internal algorithm used by the database to do the 'GROUP BY'. In higher Oracle version beginning with 10g a different algorithm is used and the results will not be sorted. So if you want a sorted result you should tell it the database by querying

SELECT     trunc(EntryDate,'MM'), COUNT(OrderNo)
FROM       Orders
GROUP BY   trunc(EntryDate,'MM')
ORDER by   trunc(EntryDate,'MM');


even if the result will be  sorted by accident.

To get exactly the output of your query execute the following statement:

SELECT     to_char(trunc(EntryDate,'MM'),'MonYY'), COUNT(OrderNo)
FROM       Orders
GROUP BY   trunc(EntryDate,'MM')
ORDER by   trunc(EntryDate,'MM');