Select distinct on one column with multiple columns returned

Question

In a table I have 2 versions of cust_id per client; what I am trying to achieve is a list of those products which are only listed under one version of the cust_id to fix the differences and output a report. I do understand that the distinct won't work because I might have the same product for multiple cust_id's.

Am trying to use DISTINICT on one column only to get a list of the distinct product_name for all cust ids.

SELECT *
FROM (
    SELECT DISTINCT
        ([product_name]),
        [cust_id] % 100000 AS 'CustId',
        COUNT([cust_id]) AS 'CustIdCount'
    FROM  [dbo].[solars_solutions_setting]
    WHERE [cust_id] IS NOT NULL
    GROUP BY
        [product_name],
        [cust_id] % 100000,
        [value]
) AS Settings WHERE Settings.CustIdCount < 2

Is it possible to output a result having three columns?

• distinct product_name
• list of all cust_id's for that product_name, comma separated (is it possible?)
• custIdCount - which should be 1 (meaning the product is only listed under one version of the cust_id)

Answer 1

Given that you are using SQL Server 2017, we can take advantage of STRING_AGG here:

SELECT
    product_name,
    STRING_AGG(cust_id, ',') AS cust_ids,
    COUNT(DISTINCT cust_id) AS dist_cust_cnt
FROM [dbo].[solars_solutions_setting]
GROUP BY
    product_name
HAVING
    COUNT(DISTINCT cust_id) > 1;

I chose to retain product names where there be more than one cust_id present. In this case, the CSV list cust_ids would have more than one value. Otherwise, it would only have a single value and the call to STRING_AGG would not serve much purpose.

Answer 2

string_agg is available in this sql sever version.

SELECT *
FROM (
    SELECT DISTINCT
        ([product_name]),
        [cust_id] % 100000 AS 'CustId',
        COUNT([cust_id]) AS 'CustIdCount',
        string_agg(cust_id, ',') as listCust
    FROM  [dbo].[solars_solutions_setting]
    WHERE [cust_id] IS NOT NULL
    GROUP BY
        [product_name],
        [cust_id] % 100000,
        [value]
) AS Settings WHERE Settings.CustIdCount < 2