How to generate rows for table Order_details, for each row in the Order_header table?

I have two tables. Order_header and Order_detail. For each row in the Order_header table, I want to generate 1 or more Order_detail rows and insert them into the Order_detail table. The number of detail rows for each header row is random, up to the number in the constant max_detailrows. How to proceed with the generate rows for Order_detail table?