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 country ( country_id number, name text, population number, area number, languages text )
TABLE: CREATE TABLE roller_coaster ( roller_coaster_id number, name text, park text, country_id number, length number, height number, speed text, opened text, status text )

### Question ###
Show the names of countries and the average speed of roller coasters from each country.

### Accurate SQL ###

SELECT T1.name, AVG(T2.speed) FROM country AS T1 JOIN roller_coaster AS T2 ON T1.country_id = T2.country_id GROUP BY T1.name