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Better performance and nicer output

In the original sample data, how come Amount in the expected result is greater than the Amount in the Effort table? Bug? 11.1 1 2012-03-04 2012-03-01 48.9 12.1 1 2012-03-11 2012-03-01 61.1 Amount for Period 3 (March) is 50, but t

No. The idea is to encourage people to find better/different solutions. By showing the reads, we display that there are other solutions.

Yes, the absence of a proper index affects all queries, bad as good. But the difference is that a good query will using the index better and thus scale better than a bad query.

One pass is one access to each and one row (or page). Self join or apply that "touches" same record twice or more is (with my definition) not a one-pass.

One pass solution (no recursion) and only one windowed function. -- Data on Dishdy's 200k row samples Table 'Worktable'. Scan count 0, logical reads 0. Table 'TC75'. Scan count 1, logical reads 624. SQL Server Execution Times: CPU time = 484 m

There has been, and Challenge 76 have index.