SQL Server 2008: TOP 10 and distinct together

Question

As the title says, I\'m using SQL Server 2008. Apologies if this question is very basic. I\'ve only been using SQL for a few days. Right now I have the following query:

Answer 1

select top 10 p.id from(select distinct p.id  from tablename)tablename

Answer 2

well I wouldn't have expected it, but Halim's SELECT distinct TOP 10 MyId FROM sometable

is functionally identical to Vaishnavi Kumar's select top 10 p.id from(select distinct p.id from tablename)tablename

create table #names ([name] varchar(10))
insert into #names ([name]) values ('jim')
insert into #names ([name]) values ('jim')
insert into #names ([name]) values ('bob')
insert into #names ([name]) values ('mary')
insert into #names ([name]) values ('bob')
insert into #names ([name]) values ('mary')
insert into #names ([name]) values ('john')
insert into #names ([name]) values ('mark')
insert into #names ([name]) values ('matthew')
insert into #names ([name]) values ('luke')
insert into #names ([name]) values ('peter')

select distinct top 5 [name] from #names

select top 5 * from (select distinct [name] from #names) subquery 

drop table #names

produces the same results for both selects:

    name
1   bob
2   jim
3   john
4   luke
5   mark

it's curious that select top 5 distinct is not valid, but select distinct top 5 is and works as you might expect select top 5 distinct to work.

Answer 3

Try

SELECT TOP 10 distinct MyId FROM sometable;

Answer 4

Few ideas:

1. You have quite a few fields in your select statement. Any value being different from another will make that row distinct.
2. TOP clauses are usually paired with WHERE clauses. Otherwise TOP doesn't mean much. Top of what? The way you specify "top of what" is to sort by using WHERE
3. It's entirely possible to get the same results even though you use TOP and DISTINCT and WHERE. Check to make sure that the data you're querying is indeed capable of being filtered and ordered in the manner you expect.

Try something like this:

SELECT DISTINCT TOP 10 p.id, pl.nm -- , pl.val, pl.txt_val
FROM dm.labs pl
JOIN mas_data.patients p    
on pl.id = p.id
where pl.nm like '%LDL%'
and val is not null
ORDER BY pl.nm

Note that i commented out some of the SELECT to limit your result set and DISTINCT logic.

Answer 5

I know this thread is old, but figured I would throw in what came up with since I just ran into this same issue. It may not be efficient, but I believe it gets the job done.

SELECT TOP 10 p.id, pl.nm, pl.val, pl.txt_val
INTO #yourTempTable
from dm.labs pl 
join mas_data.patients p on pl.id = p.id   
where pl.nm like '%LDL%' and val is not null

select p.id, pl.nm, pl.val, pl.txt_val
from #yourTempTable
where id IN (select distinct id from #yourTempTable)

Answer 6

DISTINCT removes rows if all selected values are equal. Apparently, you have entries with the same p.id but with different pl.nm (or pl.val or pl.txt_val). The answer to your question depends on which one of these values you want to show in the one row with your p.id (the first? the smallest? any?).