sql column which contains a comma separate values - sql

Question

How can I combine multiple rows into one row and have a column which contains a comma separate values?
Example: Originally my SQLresult would return the following using a simple select script like
select order_no, item_no, item_description
from orders...
order_no item_no item_description
1234 5 toaster
1234 6 hair dryer
Instead I would like to return the results into the below (having the item_description listed in the same order as the item_nos?
order_no item_nos item_descriptions
1234 5, 6 toaster, hair dryer
And could I return results like this?
order_no item_nos_descriptions
1234 5 - toaster, 6 - hair dryer
By the way I'm using SQL 2008...

Answer 1

For SQL Server 2005 and up, here's the way that I usually do it without using Recursive CTE
DECLARE #T TABLE
(
order_no int,
item_no int,
item_description nvarchar(50)
)
INSERT INTO #T VALUES (1234, 5, 'toaster')
INSERT INTO #T VALUES (1234, 6, 'hair dryer')
SELECT order_no,
STUFF(
(
SELECT ', ' + CAST(item_no AS VARCHAR) AS [text()]
FROM #T As MyItem
WHERE MyItem.order_no = MyTable.order_no
FOR XML PATH('')
), 1, 2, '' ) AS item_nos,
STUFF(
(
SELECT ', ' + CAST(item_no AS VARCHAR) AS [text()]
FROM #T As MyItem
WHERE MyItem.order_no = MyTable.order_no
FOR XML PATH('')
), 1, 2, '' ) AS item_descriptions
FROM #T AS MyTable
GROUP BY order_no
This yields:
Result Set (1 item)
order_no | item_nos | item_descriptions |
1234 | 5, 6 | 5, 6
The STUFF removes the last ', ' from the string.
The other way to do this is with recursive CTE, but I think the above will do...

Answer 2

Check out the group_concat function (docs).
select
order_no,
group_concat(item_no ORDER BY item_nos ASC SEPARATOR ', ') as item_nos,
group_concat(item_description ORDER BY item_no ASC SEPARATOR ', ')
as item_descriptions
from orders
group by order_no
will give something like this:
order_no item_nos item_descriptions
1234 5, 6 toaster, hair dryer
For the second form you requested, it would look something like this:
select
order_no,
group_concat( concat(item_no,' - ',item_description
ORDER BY item_no ASC SEPARATOR ', ')
as item_nos_descriptions
from orders
group by order_no

Answer 3

I think you should heed #pst if you can.
That said, most relational databases have a function to do exactly this. In MySQL it's group_concat. In Oracle it's wm_concat. In PostgreSQL it's string_agg. Notice it's rather unstandardized.
To use it, you would do something like this:
SELECT order_no, string_agg(item_description, ',')
FROM orders
INNER JOIN line_items ON line_item.order_id = order.id
GROUP BY order_no;
Note that not all databases have a way to get from CSV back to rows. This is something I know PostgreSQL can do. I would expect Oracle to be able to do it, but haven't checked, and I'm fairly sure that MySQL cannot, but could be mistaken.

Answer 4

Try GROUP_CONCAT if you are using mySQL:
SELECT order_no,
GROUP_CONCAT(item_no ORDER BY item_no ASC SEPARATOR ','),
GROUP_CONCAT(item_description ORDER BY item_no ASC SEPARATOR ',')
FROM Orders
GROUP BY order_no
In this way you can keep the original normalized DB schema and still get the following result:
order_no item_nos item_descriptions
1234 5, 6 toaster, hair dryer

Answer 5

For MySQL you could do this:
SELECT order_no,
GROUP_CONCAT(CONCAT(item_no,' - ',item_description) ORDER BY item_no ASC SEPARATOR ', ')
FROM Orders
GROUP BY order_no