[Koha] Need a little help with an SQL query

Gentle Reader, We want to get a list of all patrons for who we do *not *have email addresses but who are "active" (for example, have checked a book out in the last 6 months) I know how to get a list of patrons with no email address but my knowledge of SQL and the database schema aren't good enough to write the "AND have checked a book out in the last 6 months" part of the query. Is there a kind soul out there who could help? We are using Koha 17.11 Thanks and Best Regards, Chris Brown