Question

A co-worker posed this question to me, and I told them, “No, you’ll need to write a sproc for that”. But I thought I’d give them a chance and put this out to the community.

Essentially, they have a table with keys mapping to multiple values. For a report, they want to aggregate on the key and “mash” all of the values into a single field. Here’s a visual:

---  -------
Key  Value
---  -------
1    A
1    B
1    C
2    X
2    Y

The result would be as follows:

---  -------
Key  Value
---  -------
1    A,B,C
2    X,Y

They need this in SQLServer 2005. Again, I think they need to write a stored procedure, but if anyone knows a magic out-of-the-box function that does this, I’d be impressed.

Answer 1

I’m not sure if sql-server supports group_concat – but that’s what you would use in MySQL:

SELECT key, GROUP_CONCAT(value) FROM table_name GROUP BY key

I use this all the time.

Also to add to this GROUP_CONCAT by default will separate value using commas, but you can format it any way you want – interjecting text, calculations or values from other columns.