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Window Functions in PostgreSQL

Introduction
LEAD and LAG
FIRST_VALUE, LAST_VALUE, NTH_VALUE
19. LAST_VALUE(x) – practice
Summary

Instruction

The query worked fine this time. Here's one thing you should remember: while FIRST_VALUE works well with the default window frame, LAST_VALUE needs an explicit definition of the right window frame to actually make sense.

Of course, you can order by one column and return the other:

SELECT
  name,
  budget,
  LAST_VALUE(budget) OVER(
    ORDER BY opened
    ROWS BETWEEN UNBOUNDED PRECEDING
      AND UNBOUNDED FOLLOWING)
FROM website;

Here we show the budget of the most recent website (not the greatest budget).

Now, you're ready to write your own example!

Exercise

Show the statistics for website_id = 1. For each row, show the day, the number of impressions and the number of impressions on the day with the most users.

Stuck? Here's a hint!

Use LAST_VALUE(impressions) and sort by the number of users.