Insert and set value with max()+1 problems

You can use the INSERT ... SELECT statement to get the MAX()+1 value and insert at the same time:

INSERT INTO 
customers( customer_id, firstname, surname )
SELECT MAX( customer_id ) + 1, 'jim', 'sock' FROM customers;

^{Note: You need to drop the VALUES from your INSERT and make sure the SELECT selected fields match the INSERT declared fields.}