I had a very strange issue recently for the SharePoint Search queries. I had a very simple SharePoint Search Query which retrieved the results from the content database. Now if I added the Order by clause, the query returned lesser number of records than normal without the order by clause.
On further research, I found out that the column in the order by clause had null values for some records, and those records were not being returned. (Surprising J. That’s not the end of your surprises). On researching the internet I found a KB article – Kb 937208 – which seems to fix the issue and the fix has been released as part of SP1. On checking my machine I had SP1 on my machine. (Even confirmed the versions of the dll for search). Then found another Kb Article - 937775 which said that the fix of the previous Kb 937208 was installed in SP1 but needs to enabled by making a registry change.
I followed the steps in Kb 937775 and it resolved the issue. (Now that is what is King of all surprises)
The link for the kb 937775 article is:
I am also sharing the link for the 937208 kb article (for reference):-