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 dorm ( dorm_name VARCHAR, dormid VARCHAR )
TABLE: CREATE TABLE student ( stuid VARCHAR, age INTEGER )
TABLE: CREATE TABLE lives_in ( stuid VARCHAR, dormid VARCHAR )

### Question ###
Find the number of students who is older than 20 in each dorm.

### Accurate SQL ###

SELECT COUNT(*), T3.dorm_name FROM student AS T1 JOIN lives_in AS T2 ON T1.stuid = T2.stuid JOIN dorm AS T3 ON T3.dormid = T2.dormid WHERE T1.age > 20 GROUP BY T3.dorm_name