Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE tweets ( id number, uid number, text text, createdate time )
TABLE: CREATE TABLE user_profiles ( uid number, name text, email text, partitionid number, followers number )
TABLE: CREATE TABLE follows ( f1 number, f2 number )

### Question ###
Find the average number of followers for the users who had some tweets.

### Accurate SQL ###

SELECT AVG(followers) FROM user_profiles WHERE uid IN (SELECT uid FROM tweets)