A primary key should never be visible to the user, so I don't see how the ID should be related to the search. Beside, having a non-related extra field in a table is not what I consider an "improvement" ;)

>It's funny, but just a second ago I was thinking exactly the same.
>
>I created PK field as GUID, but then I thought, that for the search I may also need some sort of ID with Order record. Besides, having only PK and Date in Order table sounds a bit bare/silly, so I decided to "improve" it.