Selecting only a single row per id - sql

Question

I'd like to get back only one row per ID, even if there are multiple rows associated with an ID.
The scenario is that the data reflects a site selling land / properties, and that for each listing, there may be multiple images associated with each ID. I need only one.
Thank You.
As requested, sample data:
RowNumber ID UserID CountryID tbl_detailsID Name Description Price AddressLine1 AddressLine2 City State Zip AddressGPS Space Amenities Policies URL DateEntered DateExpires NumViews IsCompanyProperty EnforceMinStay IsOtherSite rate_Avg isFeatured DayPrice ImageURL Name check_in check_out currency bathroom_count pet unit_size elder handicap occupancy bedroom_count LinkURL smoking unit_size_Units property_Type children Minimum_stay Minimum_stay_Unit CountryName
2 247586 1 1 161398 Beautiful Oceanfront Home in Cambria California Located on the Central Coast of California 10 minutes from Hearst Castle.
Phone 1: Toll Free [phone]
Phone 2: [phone] (California, USA)
direct email contact: debbie (#) maisonsdecambria.com
Leopold Cove" is a beautiful Oceanfront Home located on the Central Coast of California. It has fabulous ocean views and access to the water from a private stairway. The living area has large plate glass windows that feature 180 degree views of the Pacific Ocean. A comfortable platform style bed & a warm, cozy fireplace are also located in the living area so you can relax for hours, or even days, enjoying the beauty that surrounds you. There is a full kitchen & a separate bedroom with 2 twin beds. The property also has a picnic area & places to sit, perhaps with a good book & a glass of wine while you watch the sunset. If you are a nature lover, you will enjoy the otters, seals & birdlife that we are privileged to have so close to us. During the gray whale migration times, this is a p 2183 Sherwood Drive Cambria California 93428 35.544712|-121.095444 http://www.flipkey.com/cambria-vacation-rentals/p202618/ 2012-10-01 10:52:00 2012-10-15 10:52:00 0 0 0 703 5.0 0 NULL http://images1.flipkey.com/img/photos/302459/243298/large_302459-243298-007-1346943508.jpg Beautiful Oceanfront Home in Cambria California USD 1 Ask 0 Ask Ask 4 1 http://www.flipkey.com/cambria-vacation-rentals/p202618/ Ask House Ask 0 NULL United States
3 247586 1 1 161398 Beautiful Oceanfront Home in Cambria California Located on the Central Coast of California 10 minutes from Hearst Castle.
Phone 1: Toll Free [phone]
Phone 2: [phone] (California, USA)
direct email contact: debbie (#) maisonsdecambria.com
Leopold Cove" is a beautiful Oceanfront Home located on the Central Coast of California. It has fabulous ocean views and access to the water from a private stairway. The living area has large plate glass windows that feature 180 degree views of the Pacific Ocean. A comfortable platform style bed & a warm, cozy fireplace are also located in the living area so you can relax for hours, or even days, enjoying the beauty that surrounds you. There is a full kitchen & a separate bedroom with 2 twin beds. The property also has a picnic area & places to sit, perhaps with a good book & a glass of wine while you watch the sunset. If you are a nature lover, you will enjoy the otters, seals & birdlife that we are privileged to have so close to us. During the gray whale migration times, this is a p 2183 Sherwood Drive Cambria California 93428 35.544712|-121.095444 http://www.flipkey.com/cambria-vacation-rentals/p202618/ 2012-10-01 10:52:00 2012-10-15 10:52:00 0 0 0 703 5.0 0 NULL http://images1.flipkey.com/img/photos/302459/243298/large_302459-243298-006-1346943508.jpg Beautiful Oceanfront Home in Cambria California USD 1 Ask 0 Ask Ask 4 1 http://www.flipkey.com/cambria-vacation-rentals/p202618/ Ask House Ask 0 NULL United States
4 247586 1 1 161398 Beautiful Oceanfront Home in Cambria California Located on the Central Coast of California 10 minutes from Hearst Castle.
Phone 1: Toll Free [phone]
Phone 2: [phone] (California, USA)
direct email contact: debbie (#) maisonsdecambria.com
Leopold Cove" is a beautiful Oceanfront Home located on the Central Coast of California. It has fabulous ocean views and access to the water from a private stairway. The living area has large plate glass windows that feature 180 degree views of the Pacific Ocean. A comfortable platform style bed & a warm, cozy fireplace are also located in the living area so you can relax for hours, or even days, enjoying the beauty that surrounds you. There is a full kitchen & a separate bedroom with 2 twin beds. The property also has a picnic area & places to sit, perhaps with a good book & a glass of wine while you watch the sunset. If you are a nature lover, you will enjoy the otters, seals & birdlife that we are privileged to have so close to us. During the gray whale migration times, this is a p 2183 Sherwood Drive Cambria California 93428 35.544712|-121.095444 http://www.flipkey.com/cambria-vacation-rentals/p202618/ 2012-10-01 10:52:00 2012-10-15 10:52:00 0 0 0 703 5.0 0 NULL http://images1.flipkey.com/img/photos/302459/243298/large_302459-243298-005-1346943508.jpg Beautiful Oceanfront Home in Cambria California USD 1 Ask 0 Ask Ask 4 1 http://www.flipkey.com/cambria-vacation-rentals/p202618/ Ask House Ask 0 NULL United States
5 247586 1 1 161398 Beautiful Oceanfront Home in Cambria California Located on the Central Coast of California 10 minutes from Hearst Castle.
Phone 1: Toll Free [phone]
Phone 2: [phone] (California, USA)
direct email contact: debbie (#) maisonsdecambria.com
Leopold Cove" is a beautiful Oceanfront Home located on the Central Coast of California. It has fabulous ocean views and access to the water from a private stairway. The living area has large plate glass windows that feature 180 degree views of the Pacific Ocean. A comfortable platform style bed & a warm, cozy fireplace are also located in the living area so you can relax for hours, or even days, enjoying the beauty that surrounds you. There is a full kitchen & a separate bedroom with 2 twin beds. The property also has a picnic area & places to sit, perhaps with a good book & a glass of wine while you watch the sunset. If you are a nature lover, you will enjoy the otters, seals & birdlife that we are privileged to have so close to us. During the gray whale migration times, this is a p 2183 Sherwood Drive Cambria California 93428 35.544712|-121.095444 http://www.flipkey.com/cambria-vacation-rentals/p202618/ 2012-10-01 10:52:00 2012-10-15 10:52:00 0 0 0 703 5.0 0 NULL http://images1.flipkey.com/img/photos/302459/243298/large_302459-243298-004-1346943508.jpg Beautiful Oceanfront Home in Cambria California USD 1 Ask 0 Ask Ask 4 1 http://www.flipkey.com/cambria-vacation-rentals/p202618/ Ask House Ask 0 NULL United States
6 247586 1 1 161398 Beautiful Oceanfront Home in Cambria California Located on the Central Coast of California 10 minutes from Hearst Castle.
Phone 1: Toll Free [phone]
Phone 2: [phone] (California, USA)
direct email contact: debbie (#) maisonsdecambria.com
Leopold Cove" is a beautiful Oceanfront Home located on the Central Coast of California. It has fabulous ocean views and access to the water from a private stairway. The living area has large plate glass windows that feature 180 degree views of the Pacific Ocean. A comfortable platform style bed & a warm, cozy fireplace are also located in the living area so you can relax for hours, or even days, enjoying the beauty that surrounds you. There is a full kitchen & a separate bedroom with 2 twin beds. The property also has a picnic area & places to sit, perhaps with a good book & a glass of wine while you watch the sunset. If you are a nature lover, you will enjoy the otters, seals & birdlife that we are privileged to have so close to us. During the gray whale migration times, this is a p 2183 Sherwood Drive Cambria California 93428 35.544712|-121.095444 http://www.flipkey.com/cambria-vacation-rentals/p202618/ 2012-10-01 10:52:00 2012-10-15 10:52:00 0 0 0 703 5.0 0 NULL http://images1.flipkey.com/img/photos/302459/243298/large_302459-243298-003-1346943508.jpg Beautiful Oceanfront Home in Cambria California USD 1 Ask 0 Ask Ask 4 1 http://www.flipkey.com/cambria-vacation-rentals/p202618/ Ask House Ask 0 NULL United States
7 247586 1 1 161398 Beautiful Oceanfront Home in Cambria California Located on the Central Coast of California 10 minutes from Hearst Castle.
Phone 1: Toll Free [phone]
Phone 2: [phone] (California, USA)
direct email contact: debbie (#) maisonsdecambria.com
Leopold Cove" is a beautiful Oceanfront Home located on the Central Coast of California. It has fabulous ocean views and access to the water from a private stairway. The living area has large plate glass windows that feature 180 degree views of the Pacific Ocean. A comfortable platform style bed & a warm, cozy fireplace are also located in the living area so you can relax for hours, or even days, enjoying the beauty that surrounds you. There is a full kitchen & a separate bedroom with 2 twin beds. The property also has a picnic area & places to sit, perhaps with a good book & a glass of wine while you watch the sunset. If you are a nature lover, you will enjoy the otters, seals & birdlife that we are privileged to have so close to us. During the gray whale migration times, this is a p 2183 Sherwood Drive Cambria California 93428 35.544712|-121.095444 http://www.flipkey.com/cambria-vacation-rentals/p202618/ 2012-10-01 10:52:00 2012-10-15 10:52:00 0 0 0 703 5.0 0 NULL http://images1.flipkey.com/img/photos/302459/243298/large_302459-243298-002-1346943508.jpg Beautiful Oceanfront Home in Cambria California USD 1 Ask 0 Ask Ask 4 1 http://www.flipkey.com/cambria-vacation-rentals/p202618/ Ask House Ask 0 NULL United States
8 247586 1 1 161398 Beautiful Oceanfront Home in Cambria California Located on the Central Coast of California 10 minutes from Hearst Castle.
Phone 1: Toll Free [phone]
Phone 2: [phone] (California, USA)
direct email contact: debbie (#) maisonsdecambria.com
Leopold Cove" is a beautiful Oceanfront Home located on the Central Coast of California. It has fabulous ocean views and access to the water from a private stairway. The living area has large plate glass windows that feature 180 degree views of the Pacific Ocean. A comfortable platform style bed & a warm, cozy fireplace are also located in the living area so you can relax for hours, or even days, enjoying the beauty that surrounds you. There is a full kitchen & a separate bedroom with 2 twin beds. The property also has a picnic area & places to sit, perhaps with a good book & a glass of wine while you watch the sunset. If you are a nature lover, you will enjoy the otters, seals & birdlife that we are privileged to have so close to us. During the gray whale migration times, this is a p 2183 Sherwood Drive Cambria California 93428 35.544712|-121.095444 http://www.flipkey.com/cambria-vacation-rentals/p202618/ 2012-10-01 10:52:00 2012-10-15 10:52:00 0 0 0 703 5.0 0 NULL http://images1.flipkey.com/img/photos/302459/243298/large_302459-243298-001-1346943508.jpg Beautiful Oceanfront Home in Cambria California USD 1 Ask 0 Ask Ask 4 1 http://www.flipkey.com/cambria-vacation-rentals/p202618/ Ask House Ask 0 NULL United States
And the Omni-query I that I am constructing to replace a few hundred lines of temp tables:
SELECT DISTINCT ROW_NUMBER() OVER(ORDER BY tbl_Properties.ID DESC) AS [RowNumber], tbl_Properties.ID, tbl_Properties.UserID, tbl_Properties.CountryID, tbl_Properties.tbl_detailsID, tbl_Properties.Name,
tbl_Properties.[Description], tbl_Properties.Price, tbl_Properties.AddressLine1, tbl_Properties.AddressLine2, tbl_Properties.City, tbl_Properties.[State], tbl_Properties.Zip, tbl_Properties.AddressGPS,
tbl_Properties.[Space],
tbl_Properties.Amenities,
tbl_Properties.Policies,
tbl_Properties.URL,
tbl_Properties.DateEntered,
tbl_Properties.DateExpires,
tbl_Properties.NumViews,
tbl_Properties.IsCompanyProperty,
tbl_Properties.EnforceMinStay,
tbl_Properties.IsOtherSite,
tbl_Properties.rate_Avg,
tbl_Properties.isFeatured,
tbl_Properties.DayPrice,
tbl_Images.ImageURL,
tbl_Details.Name,
tbl_Details.check_in,
tbl_Details.check_out,
tbl_Details.currency,
tbl_Details.bathroom_count,
tbl_Details.pet,
tbl_Details.unit_size,
tbl_Details.elder,
tbl_Details.handicap,
tbl_Details.occupancy,
tbl_Details.bedroom_count,
tbl_Details.url As [LinkURL],
tbl_Details.smoking,
tbl_Details.unit_size_Units,
tbl_Details.property_Type,
tbl_Details.children,
tbl_Details.Minimum_stay,
tbl_Details.Minimum_stay_Unit,
tbl_Countries.Name As [CountryName]
FROM [tbl_Details]
INNER JOIN [tbl_Properties] ON [tbl_Details].[detailsID] = [tbl_Properties].[tbl_detailsID]
INNER JOIN [tbl_Images] ON [tbl_Images].PropertyID = [tbl_Properties].ID
INNER JOIN [tbl_Countries] ON [tbl_Countries].ID = [tbl_Properties].CountryID
The query itself is, of course, not finished yet.

Answer 1

If your SQLServer version supports row_number() OVER (2008,2012 support)
select * from
(select t.*,
row_number() over (partition by id order by id) as rownumber from t
) t1
where t1.rownumber=1
Here is the SQLFiddle example

Answer 2

Since there's no sample data you'll need to bend this response to suit your needs
select
Listings.*, SingleImage.Column1, SingleImage.Column2
from Listings
cross apply (
select top 1 *
from Images
where Listings.ListingID = Images.ListingID
) SingleImage
That needs SQL 2005 or newer (for the "cross apply" to work)
There are ways to make it work in SQL 2000 too but they're not as efficient

Answer 3

try this:
SELECT TOP 1 * FROM
imagestable
WHERE imagestable.landID = <theID>
This will return the first image in the table that belongs to the property.
You can INNER JOIN this query with your property table if you want to return all property info as a single record.

Answer 4

In SQL Server 2005+ you can use this
use tempdb
go
create table tbl (id int, s varchar(50))
insert into tbl values (1,'qwe'),(1,'asd'), (1,'qwff'),(2,'ert'),(2,'ykf'),(3,'')
;with cte
AS
(
SELECT id,s, ROW_NUMBER() OVER (PARTITION BY id ORDER BY s ) n
FROM tbl
)
SELECT id,s
FROM CTE
WHERE n=1
drop table tbl