Which of the following is the correct syntax to get the last value of a column score ordered by date using LAST_VALUE in PostgreSQL?

easy📝 Syntax Q12 of 15

PostgreSQL - Window Functions in PostgreSQL

Which of the following is the correct syntax to get the last value of a column score ordered by date using LAST_VALUE in PostgreSQL?

ASELECT LAST_VALUE(score) FROM results ORDER BY date;

BSELECT LAST_VALUE(score) OVER (ORDER BY date ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) FROM results;

CSELECT LAST_VALUE(score) OVER (PARTITION BY date) FROM results;

DSELECT LAST_VALUE(score) OVER (ORDER BY date) FROM results;

Step-by-Step Solution

Solution:

Step 1: Understand LAST_VALUE default frame
LAST_VALUE by default looks from current row to end, so it may not return the last value overall without framing.
Step 2: Use explicit window frame to get true last value
Adding ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING ensures the entire partition is considered.
Final Answer:
SELECT LAST_VALUE(score) OVER (ORDER BY date ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) FROM results; -> Option B
Quick Check:
LAST_VALUE needs full frame to get last value [OK]

Quick Trick: Add full window frame to LAST_VALUE for correct last row [OK]

Common Mistakes:

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