Getting Error when try to use sql query

[Jorge Carlos Guedert Junior]

I'm getting error


{"result-set":{"docs":[{"EXCEPTION":"java.util.Date cannot be cast to 
java.lang.String","EOF":true,"RESPONSE_TIME":68}]}}


when i trying to do this query:

SELECT `date` as Date, COUNT(deviceSerialNumber) FROM `trip-day-mobile` GROUP 
BY `date`?


this problem occurs only when i group by date if not grouped return values 
normally


Solr Version: 6.6