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Jak pisać funkcje okna SQL za pomocą quizu AI

Sprawdź partycje okna SQL, powiązania rankingowe i łączną liczbę klatek z przykładami zakupów, brakującymi datami i wyborem najnowszych wydarzeń.

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Pytanie 1 z 8

For ordered purchases of 5, 7 and 4, which row-by-row running totals match the guide's frame?

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Odpowiedzi i wyjaśnienia pojawiają się w miarę rozwiązywania quizu.

  1. For ordered purchases of 5, 7 and 4, which row-by-row running totals match the guide's frame?
    • 5, 7 and 4
    • 5, 12 and 16
    • 16, 16 and 16
    • 5, 14 and 12
  2. For descending scores 100, 100 and 90, which sequence does RANK produce?
    • 1, 2 and 3
    • 1, 1 and 2
    • 2, 2 and 3
    • 1, 1 and 3
  3. Which function gives tied scores 100, 100 and 90 the ranks 1, 1 and 2?
    • DENSE_RANK
    • ROW_NUMBER
    • RANK
    • LAG
  4. A latest-event query uses ROW_NUMBER ordered only by a timestamp shared by two events. What is needed for a predictable choice between them?
    • Remove the account partition
    • Replace the final result with an unqualified DISTINCT
    • Add an appropriate tie-breaker to the window ordering
    • Assume insertion order resolves every tie
  5. Why can LAG of daily sales fail to represent yesterday's sales?
    • LAG always refers to the first row of the entire table
    • The previous recorded row may be separated by missing dates
    • LAG automatically groups all dates in one month
    • The function replaces missing dates with zero
  6. An ORDER BY appears inside OVER. What is still needed if the final displayed result must have a specified order?
    • Only a PARTITION BY with the same column
    • Only a ROWS frame using the same ordering column
    • No further clause because window ordering guarantees display order
    • A final ORDER BY for the query result
  7. Why should a tie-breaker not be added indiscriminately to RANK when equal scores should share a rank?
    • It can change which rows are peers and therefore change tied ranks
    • It leaves peer membership unchanged because only the first ordering column matters
    • It changes only the final display order and never the window calculation
    • It preserves equal-score ranks while automatically making their row numbers predictable
  8. In PostgreSQL, how can a query filter rows using a window value calculated in an inner SELECT?
    • Use that value in the same SELECT's WHERE without another query level
    • Replace OVER with GROUP BY in every case
    • Filter in an outer query or common table expression
    • Assume every database supports an identical QUALIFY clause