How to add condition in custom report query where clause to get records created in Last Quarter

You should be able to use interval to get the last quarter. 

SELECT DATE_ADD('2008-01-02', INTERVAL 31 DAY);

https://dev.mysql.com/doc/refman/8.0/en/date-and-time-functions.html 

You should be able to use interval to get the last quarter. 

SELECT DATE_ADD('2008-01-02', INTERVAL 31 DAY);

https://dev.mysql.com/doc/refman/8.0/en/date-and-time-functions.html