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

You could use a Common Table Expression to get the top 10 distinct ID's and then join those to the rest of your data:

;WITH TopTenIDs AS
( 
   SELECT DISTINCT TOP 10 id
   FROM dm.labs 
   ORDER BY ......
)
SELECT 
    tti.id, pl.nm, pl.val, pl.txt_val
FROM
    TopTenIDs tti
INNER JOIN
    dm.labs pl ON pl.id = tti.id
INNER JOIN 
    mas_data.patients p ON pl.id = p.id
WHERE
    pl.nm like '%LDL%'
    AND val IS NOT NULL

That should work. Mind you: if you have a "TOP x" clause, you typically also need an ORDER BY clause - if you want the TOP 10, you need to tell the system in what order that "TOP" is.

PS: why do you even join the "patients" table, if you never select any fields from it??

Answer 2

This is the right answer and you can find 3 heights value from table

SELECT TOP(1)  T.id FROM (SELECT DISTINCT TOP(3) st.id  FROM Table1 AS t1 , Table2 AS t2 WHERE t1.id=t2.id ORDER BY (t2.id) DESC ) T ORDER BY(T.id) ASC

Answer 3

I think the problem is that you want one result for each p.id?

But you are getting "duplicate" results for some p.id's, is that right?

The DISTINCT keyword applies to the entire result set, so applies to pl.nm, pl.val, pl.txt_val, not just p.id.

You need something like

SELECT TOP 10 p.id, max( p1.nm ), max (p1.val), ...
FROM ...
GROUP BY p.id

Won't need the distinct keyword then.

Answer 4

SELECT TOP 14 A, B, C
  FROM MyDatabase
  Where EXISTS 
   (
     Select Distinct[A] FROM MyDatabase
    )

Answer 5

SELECT DISTINCT * FROM (

SELECT 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

)

Answer 6

The easy option is to use group by and select min/max for all other fields

SELECT TOP 10 
    p.id, 
    max(pl.nm),
    max(pl.val),
    max(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
group by 
    p.id

This can get quite tedious for wide table so the other option is to use rank over and partiion

SELECT TOP 10 
    p.id, 
     pl.nm, 
     pl.val, 
   pl.txt_val, 
    rank() over(partition by p.id order by p.id) as Rank
from 
    dm.labs pl
join 
    mas_data.patients p    
on 
    pl.id = p.id
  where 
    pl.nm like '%LDL%'
and 
    val is not null
and
    Rank = 1