Question

Suppose there was a SQL table like this:

Label Name | Last name | Address Line 1 | Address line 2
-----------+-----------+----------------+-------------------
John       | Smith     | 100 Any St     | Anytown, WI, 50000
Jane       | Smith     | 100 Any St     | Anytown, WI, 50000
Bill       | Doe       | 200 Any St     | Anytown, WI, 50000
Sam        | Rodgers   | 200 Any St     | Anytown, WI, 50000
Lisa       | Thompson  | 300 Any St     | Anytown, WI, 50000
Walter     | Thompson  | 300 Any St     | Anytown, WI, 50000
Chuck      | Thompson  | 300 Any St     | Anytown, WI, 50000

What SQL query would produce a table like this?:

Label Name              | Last name | Address Line 1 | Address line 2
------------------------+-----------+----------------+-------------------
John and Jane           | Smith     | 100 Any St     | Anytown, WI, 50000
Bill                    | Doe       | 200 Any St     | Anytown, WI, 50000
Sam                     | Rodgers   | 200 Any St     | Anytown, WI, 50000
Lisa, Walter, and Chuck | Thompson  | 300 Any St     | Anytown, WI, 50000

Answer 1

You should do these kinds of things in the presentation layer, rather than in the DBMS.

But if you really want to do this at the DBMS level, and your DBMS is MS SQL Server (as your comment seems to indicate), you can do the following:

First, create a function that concatenates related [Label Name] values (using ‘,’ and ‘and’ as separators):

CREATE FUNCTION CombineNames (
    @LastName nvarchar(max),
    @AddressLine1 nvarchar(max),
    @AddressLine2 nvarchar(max)
)
RETURNS nvarchar(max) AS
BEGIN

    DECLARE @NameCount INT;

    SELECT @NameCount = COUNT(*)
    FROM YOUR_TABLE
    WHERE
        [Last name] = @LastName
        AND [Address Line 1] = @AddressLine1
        AND [Address line 2] = @AddressLine2;

    DECLARE @List nvarchar(max);

    SELECT
        @List
            = COALESCE(@List, '')
            + (
                CASE ROW_NUMBER() OVER(ORDER BY [Label Name])
                WHEN 1 THEN ''
                WHEN @NameCount THEN ' and '
                ELSE ', '
                END
            )
            + CAST([Label Name] as nvarchar(max))
    FROM YOUR_TABLE
    WHERE
        [Last name] = @LastName
        AND [Address Line 1] = @AddressLine1
        AND [Address line 2] = @AddressLine2
    ORDER BY
        [Label Name];

    RETURN (SELECT @List)

END

Then use the function like this:

SELECT
    dbo.CombineNames([Last name], [Address Line 1], [Address Line 2]),
    T.*
FROM
    (
        SELECT DISTINCT [Last name], [Address Line 1], [Address Line 2]
        FROM YOUR_TABLE
    ) T

Result:

(No column name)        Last name       Address Line 1      Address Line 2
----------------        ---------       --------------      --------------
Bill                    Doe             200 Any St          Anytown, WI, 50000
Sam                     Rodgers         200 Any St          Anytown, WI, 50000
Jane and John           Smith           100 Any St          Anytown, WI, 50000
Chuck, Lisa and Walter  Thompson        300 Any St          Anytown, WI, 50000