instruction: maximum single-day reputation gain ever.
response: SELECT MAX(Rep) AS MaxRep, OwnerDisplayName, OwnerUserId, DateReputation FROM (SELECT SUM(Score) AS Rep, OwnerDisplayName, OwnerUserId, CAST(TIME_TO_STR(CreationDate, '%m/%d/%Y') AS TEXT(30)) AS DateReputation FROM Posts GROUP BY OwnerDisplayName, OwnerUserId, CAST(TIME_TO_STR(CreationDate, '%m/%d/%Y') AS TEXT(30))) AS a GROUP BY OwnerDisplayName, OwnerUserId, DateReputation ORDER BY MaxRep DESC LIMIT 50