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 customer_contact_channels ( active_to_date VARCHAR, active_from_date VARCHAR )

### Question ###
What is the average time span of contact channels in the database?

### Accurate SQL ###

SELECT AVG(active_to_date - active_from_date) FROM customer_contact_channels