instruction: Evolution of the up-/downvote ratio by year and month. Look at the Graph, to see the evolution of the upvote/downvote ratio.
response: SELECT DATEFROMPARTS(YEAR(CreationDate), MONTH(CreationDate), 1) AS YearMonth, (CAST(SUM(CASE WHEN VoteTypeId = 2 THEN 1 ELSE 0 END) AS FLOAT) / NULLIF(CAST(SUM(CASE WHEN VoteTypeId = 3 THEN 1 ELSE 0 END) AS FLOAT), 0)) AS Ratio FROM Votes WHERE CreationDate > '01-01-2015' AND CreationDate < '12-31-2020' GROUP BY DATEFROMPARTS(YEAR(CreationDate), MONTH(CreationDate), 1) ORDER BY DATEFROMPARTS(YEAR(CreationDate), MONTH(CreationDate), 1)