Hello Kunal ,
After the discuss , I checked on my env , and i found that the sd_row column in usm_subscription_detail table is used to group the items in each request_item ( or service option ) of a request .
Please check the screenshot from my env .
when you query usm_subscription_details based on request_id, if you group ( i.e order by ) sd_row , you will be able to see clearly ALL the items for each request item of a request . In each request item , the first entry's id of ALL those items represents this request item .
Let me know if it answers your question .
Thanks, Jing