A bad user is one who never tweeted or retweeted. Write a query to find the usernames of bad users. Try using Not Exists.

Tables Schema as Below:

users

columnName dataType

id int

username varchar

email varchar

remember$\_$token varchar

created$\_$at datetime

updated$\_$at datetime

password$\_$digest varchar

tweets

columnName dataType

id int

content varchar

created$\_$at datetime

updated$\_$at datetime

UserTweetRelation

columnName dataType

id int

created$\_$at datetime

retweet boolean

user$\_$id varchar

tweet$\_$id varchar

relationships

columnName dataType

id int

created$\_$at datetime

updated$\_$at datetime

follower$\_$id int

followed$\_$id int