How many tweets are there?
select count(*) from tweets
What is the text of the tweet with id 1?
select text from tweets where id = 1
How many tweets does each user have?
select t1.name, count(*) from user_profiles as t1 join tweets as t2 on t1.uid = t2.uid group by t2.uid
Who has more than one tweet?
select t1.name from user_profiles as t1 join tweets as t2 on t1.uid = t2.uid group by t2.uid having count(*) > 1