Priority of order in Syntax for where, group by, having, order by

There are particular sequence in sql syntax as per follows: 

SELECT ...

WHERE..

GROUP BY..

HAVING

ORDER BY...DESC

Example 

SELECT strftime('%H',timestamp) as Hours , round(AVG(score),0), COUNT(*) as Count_of_Stories FROM hacker_news 

where timestamp is NOT NULL

GROUP BY 1 

ORDER BY 1