Windowing to the max
The Idaho field staff has been reporting back sample data for a variety of measures in their water system monitoring system. They'd like you to compare the Alkalinity samples to the maximum for that year to help them analyze trends towards the maximum. The data is kinda messy and you'll have to explicitly convert any dates.
Diese Übung ist Teil des Kurses
Introduction to Redshift
Anleitung zur Übung
- Explicitly convert the
sample_dateto a date aliased asdate_sampledand order by it. - Use a window function to calculate the max Alkalinity reading,
characteristic_measurementvalue, for the year.
Interaktive Übung
Versuche dich an dieser Übung, indem du diesen Beispielcode vervollständigst.
SELECT fk_monitoringlocation,
-- Explicitly convert sample_date to a DATE
___(sample_date AS ___) as date_sampled,
characteristic_measurementvalue,
-- Find the max measurement
___(___) ___ (
-- For each year window based on the sample date
___ BY DATE_PART(___, ___(___ AS DATE))
) as yearly_max
FROM public_intro_redshift.idaho_samples
WHERE characteristic_name = 'Alkalinity'
ORDER BY date_sampled DESC,
fk_monitoringlocation;