>>>
>>>When you run this query with Actual Execution plan information, what you get?
>>
>>I don't know what exactly to tell you. I get an Execution Plan tab displayed with some graphical stuff in it but no particular message that I can tell you. What do you need to know?
>
>You have the best performance when you have [index seek] in Execution plan, worst is when you have [Table Scan].
>Try to remove WHERE and see if you get this faster.
>If yes, then should think about workaround.

I removed the where and it wasn't noticeably faster. Update: it actually was about 10 seconds faster, without was 20 seconds and with was 30.

The execution plan shows index seeks mostly but a couple "Key Lookup (Clustered)"

One of those shows as 81% for "Invoices.PK_Invoices"