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 staff ( phone_number VARCHAR )
TABLE: CREATE TABLE customers ( phone_number VARCHAR )

### Question ###
Find the phone number of all the customers and staff.

### Accurate SQL ###

SELECT phone_number FROM customers UNION SELECT phone_number FROM staff