How to Join a table to a group_contact in mySql I have this query

select concat('[',group_concat(inn.str),']') into string4  from (
        select concat(
            '{"idmm":',customer.id,
            ',"cd":"',customer.code,
            '","nm":"',customer.name,

            '"," Order":"', 

            '","des":"', customer.description,                   
            '"}' )as a_string
        from
            customertable customer

    ) 


How do I join the Order table to have the order_name joined to the string?
In the middle of the above string you see '"," Order":"', right? I want to join the Order table to pull the order_name as the customertable has order_id and concatenate to the string.

The customertable has columns

id int(10)  
order_id int(10)  
code char(6) 
name varchar(45) 
description varchar(500)


and Ordertable has columns

order_id int(10) 
order_name varchar(500)
FROM Customers c
JOIN Orders o USING(order_id)