Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
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?
### Answer:
SELECT AVG(active_to_date - active_from_date) FROM customer_contact_channels