So far the window we have used inside our query has been static. However, for calculations such as a moving average, this is not enough. A moving average needs a sliding window that moves along as data is processed.
Here is an example of how a moving average can be achieved:
test=# SELECT country, year, production,
min(production) OVER (PARTITION BY country ORDER BY year ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
FROM t_oil
WHERE year BETWEEN 1978 AND 1983
AND country IN ('Iran', 'Oman'); country | year | production | min ---------+-------+------------+------ Iran | 1978 | 5302 | 3218 Iran | 1979 | 3218 | 1479 Iran | 1980 | 1479 | 1321 Iran | 1981 | 1321 | 1321 Iran | 1982 | 2397 | 1321 Iran | 1983 | 2454 | 2397 Oman ...
