Is ORDER BY and ROW_NUMBER() deterministic?

Question

I\'ve used SQL in couple databases engines from time to time several years but have little theoretical knowledge so my question could be very \"noobish\" for some of you. Bu

Answer 1

The general answer to any sql question "what order does this output in" is "whatever the server feels like, and it may not be the same from query to query" unless you have specifically requested a order.

Even something simple like 'select top 1000 myColumn from myTable' can come back with any rows in any order; eg the server can use parallel threads and the first thread to start returning results started reading in the middle of the table, or an index was used which included myColumn, so you got the rows with the alphabetically first productName (this time; last time the index had different stats so it selected a different index and gave you the 1000 oldest transactions)...

It is even theoretically possible for the server to say "i had these 10 pages in my memory cache that match your query, i'll pass you these ones while i wait for the disk to return the rest...