I think you have misunderstood how the query engine in SQL Server works. One query is always one query, what is interesting is to look at the execution plans that SQL Server choose for exeuting the query. Both of our queries will probably result in similar plans (with the same physical join operation in most cases) and therefore perform more or less the same. However your query will always need a filter operator before outputting the results, which will cause it to perform slightly worse when there is a lot of rows returned.