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 employees (department_id VARCHAR, salary INTEGER, commission_pct VARCHAR)

### Question ###
display the average salary of employees for each department who gets a commission percentage.

### Accurate SQL ###

SELECT department_id, AVG(salary) FROM employees WHERE commission_pct <> "null" GROUP BY department_id