Applying the function against the column makes the entire expression non-sargable – leading to a full scan.It is not the same query, since it is now looking for 365 day boundaries to have passed, as opposed to being greater than a specific point in time 365 days ago.And while it eliminated the loop join, there are two major problems with this predicate: This got a better estimate (the typical 30% inequality guess) so not quite right. WHERE DATEDIFF ( DAY, , SYSUTCDATETIME ( ) ) <= 365
