In the last SQLskills Insider demo video I went through a scenario where you can use the query_hash column from sys.dm_exec_query_stats to aggregate statistics for queries that only differ by literal values.
I received an interesting question from someone who watched the video, ran the demo query in production and saw a 0x0000000000000000 value as the highest consumer of worker time (and also had the highest execution count).
I asked this person to show me the query text where [query_hash] = 0x0000000000000000 and it ended up being a series of FETCH NEXT and FETCH API_CURSOR calls, for example:
There may be other circumstances where 0x0000000000000000 may manifest – but I haven’t witnessed them or heard of them. If you have non-cursor scenarios where 0x0000000000000000 occurs, please share in the comments.