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WITH tab as (SELECT EXTRACT(month from creation_date::date) as month, COUNT(id) FROM stackoverflow.posts WHERE creation_date >'2008-07-31' and creation_date <'2009-01-01' GROUP BY EXTRACT(month from creation_date::date)), tab2 as(SELECT month, count, ROUND((((count - LAG(count) OVER (ORDER BY month))::numeric)/LAG(count) OVER ())*100,2) FROM tab) --WHERE month!=7 and month !=8 SELECT * FROM tab2 WHERE month!=7 and month!=8