The index is not sorted by itemNo.

It is sorted by date.

So you dont have an index on data sorted by itemno.

Imagine a phonebook sorted by Lastname, Then by firstname, then by address.

Your index will be (surname,Firstname,Address)

So I cannot search based on address because the phone book is sorted by surname, it is only possible to search by address if I already have the surname and firstname.

Same thing here.

Your phone book is sorted by date, then by ID then by number and not by ItemNo /Address, as an analogy.