If contact number is the only column that may have duplicates, you can also do it like this.
DECLARE @temp TABLE(id int, name varchar(50), age int, contact_number varchar(50));
insert into @temp(id,name) select 1,'John';
insert into @temp(id,age) select 1,34;
insert into @temp(id,contact_number) select 1,'222-444-5555';
insert into @temp(id,contact_number) select 1,'333-444-5555';
SELECT id, name, age, contact_number
FROM
(
SELECT id
,name=MAX(name) OVER (PARTITION BY id)
,age=MAX(age) OVER (PARTITION BY id)
,contact_number
FROM @temp
) a
WHERE contact_number IS NOT NULL;
My thought question: Have you ever been told that your query runs too fast?
My advice:
INDEXing a poor-performing query is like putting sugar on cat food. Yeah, it probably tastes better but are you sure you want to eat it?
The path of least resistance can be a slippery slope. Take care that fixing your fixes of fixes doesn't snowball and end up costing you more than fixing the root cause would have in the first place.
Need to UNPIVOT? Why not CROSS APPLY VALUES instead?[/url]
Since random numbers are too important to be left to chance, let's generate some![/url]
Learn to understand recursive CTEs by example.[/url]
[url url=http://www.sqlservercentral.com/articles/St