Archive Database Step 6: Include the Zeroes

Write a query listing every author with the number of books held, including the authors with none, showing 0 rather than omitting them. Get the COUNT right: check specifically that an author with no books shows 0 and not 1. Then write the anti-join version listing only the authors with nothing, and confirm the two agree. A report that silently omits the empty cases is the most common quiet error in reporting, and now you have written both versions and seen the difference.