How to create this CSV in Sql query?

Question

I have a order_detail table with the primary key order_detail_id and the foregin keys order_id and product_id. Also I have three other fields, A, B and C, to describe the nature of this order detail. A product_id can be existed on different order_id
but not in a single order_id (ie no duplicate product_id on a order). What I want the dataset to return is when passing the order_id, it could be single or multiple order_id, the query will give me the order_detail_id in comma seperate string if two or more
of the same product_id found on the multiple order_ids and the same value on the other three fields, A, B and C, ie I would like to group by all the order_detail_id in a single row if those conditions are met.  Thanks a million. 
Kahlua

Answer 1

Please post DDL, so that people do not have to guess what the keys, constraints, Declarative Referential Integrity, data types, etc. in your schema are. Learn how to follow ISO-11179 data element naming conventions and formatting rules. Temporal data should
use ISO-8601 formats. Code should be in Standard SQL as much as possible and not local dialect. 
This is minimal polite behavior on SQL forums. 
>> I have a order_detail table with the PRIMARY KEY order_detail_id and the foreign keys order_id and product_id. <<
WRONG. Order details are called weak entities in data modeling. They need a strong entity (the order) to exist. Therefore, the key has to include the order id as part of the PRIMARY KEY. There is no separate  “order_detail_id” in a correct model. 
>> Also I have three other fields [sic], A, B and C, to describe the nature of this order detail. A product_id can existed on different order_id but not in a single order_id (i.e. no duplicate product_id on a order). <<
Columns are not anything like fields. You need to learn basic terms. Here is what a polite person might have posted:
CREATE TABLE Orders
(order_nbr CHAR(15) NOT NULL PRIMARY KEY, 
CREATE TABLE Order_Details
(order_nbr CHAR(15) NOT NULL 
   REFERENCES Orders(order_nbr)
   ON DELETE CASCADE, 
 product_id CHAR(15) NOT NULL,
 PRIMARY KEY (order_nbr, product_id),
 order_qty INTEGER DEFAULT 1 NOT NULL
   CHECK (order_qty > 0), 
 -- special attributes
  alpha CHAR(5) NOT NULL,
  beta CHAR(5) NOT NULL,
  gamma CHAR(5) NOT NULL,
>> What I want the data set to return is when passing the order_id, it could be single or multiple order_id, the query will give me the order_detail_id in comma separate string if two or more of the same product_id found on the multiple order_ids and
the same value on the other three fields [sic], A, B and C, i.e. I would like to group by all the order_detail_id in a single row if those conditions are met. <<
WRONG! You want to violate First Normal Form (1NF) and do display formatting in the database! You have not ever read a book or had a class on RDBMS. CSV? No! 
Now, where is the sample data? More bad Netiquette! I have done this before; you can read the details at: 
http://www.tdan.com/view-perspectives/5343
It is a special case of a relational division. Since you did not post DDL, I will not post DML. 
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