It's possible, as the other commenters mentioned, it would come down to reviewing the query plan. I was just trying to address the two parts of your original c

It's possible, as the other commenters mentioned, it would come down to reviewing the query plan. I was just trying to address the two parts of your original comment, which were "is very baffeling" and "left join performance in sql server is very bad in some situations.". Hopefully my answer helped to un-baffel a little.