Select Only one row where Address Matches - sql

Question

Using SQL Server, I have a Contact table that contains the name and address of my contacts. I have several instances of multiple contacts living at the same address. When sending my newsletter, I only want to send it to each address one time. How can I modify the query below to only display the first contact at each address?
SELECT
dbo_Contact.Contact_Title AS Title,
dbo_Contact.Contact_FirstName AS [First Name],
dbo_Contact.Contact_LastName AS [Last Name],
dbo_Contact.Contact_Suffix AS Suffix,
dbo_Contact.Business_Name AS [Business Name],
dbo_Contact.Contact_Address1 AS [Address 1],
dbo_Contact.Contact_Address2 AS [Address 2],
dbo_Contact.Contact_City AS City,
dbo_Contact.Contact_State AS State,
dbo_Contact.Contact_Zip AS Zip,
dbo_Contact.Contact_Email AS Email
FROM
dbo_Contact
INNER JOIN
dbo_Mailing_Subscribers ON dbo_Contact.[ContactID] = dbo_Mailing_Subscribers.[ContactID]
WHERE
(((dbo_Contact.Contact_Inactive) = False)
AND ((dbo_Mailing_Subscribers.Mailing_ID) = True)
AND ((dbo_Mailing_Subscribers.Subscribed) = True));
For example, if Kurt and William live at 123 A Street and Steve lives at 123 B Avenue, I would only want to return records for Kurt and Steve.

Answer 1

Okay, here is my solution.
1 - Use table aliases to reduce code foot print.
2 - Changed true/false to 1/0 to meet TSQL Boolean values.
3 - Create RowNum partition by address1, address2, zip code order by last name, first name.
4 - Select only one row from the duplicates.
;
with cteData as
(
SELECT
C.Contact_Title AS Title,
C.Contact_FirstName AS [First Name],
C.Contact_LastName AS [Last Name],
C.Contact_Suffix AS Suffix,
C.Business_Name AS [Business Name],
C.Contact_Address1 AS [Address 1],
C.Contact_Address2 AS [Address 2],
C.Contact_City AS City,
C.Contact_State AS State,
C.Contact_Zip AS Zip,
C.Contact_Email AS Email,
row_number() over (partition by Contact_Address1, Contact_Address2, Contact_Zip
order by Contact_LastName, Contact_FirstName) as RowNum
FROM
dbo_Contact as C
INNER JOIN
dbo_Mailing_Subscribers as S
ON C.[ContactID] = S.[ContactID]
WHERE
C.Contact_Inactive = 0 AND
S.Mailing_ID = 1 AND
S.Subscribed = 1
)
select * from cteData where RowNum = 1;
In short, one mailing will go out to the person with the last / first name closets to A.

Answer 2

You can do use row_number() and a subquery:
select <list of columns you want>
from (SELECT row_number() over (partition by Contact_Address1, Contact_Address2, Contact_Zip
order by ContactId
) as seqnum
dbo_Contact.Contact_Title AS Title,
dbo_Contact.Contact_FirstName AS [First Name],
dbo_Contact.Contact_LastName AS [Last Name],
dbo_Contact.Contact_Suffix AS Suffix,
dbo_Contact.Business_Name AS [Business Name],
dbo_Contact.Contact_Address1 AS [Address 1],
dbo_Contact.Contact_Address2 AS [Address 2],
dbo_Contact.Contact_City AS City,
dbo_Contact.Contact_State AS State,
dbo_Contact.Contact_Zip AS Zip,
dbo_Contact.Contact_Email AS Email
FROM dbo_Contact
INNER JOIN
dbo_Mailing_Subscribers ON dbo_Contact.[ContactID] = dbo_Mailing_Subscribers.[ContactID]
WHERE
(((dbo_Contact.Contact_Inactive) = False)
AND ((dbo_Mailing_Subscribers.Mailing_ID) = True)
AND ((dbo_Mailing_Subscribers.Subscribed) = True))
) t
where seqnum = 1;
It is unclear what you mean by the "same address" and by "the first contact". For address, the query uses the two address lines and the zip code. FOr "first contact" the query uses the lowest id in the contact table.