SQL Server Query for Rank (RowNumber) and Groupings

Question

I have a table that has some columns: User, Category, Value

And I want to make a query that will give me a ranking, of all the users by the value, but reset for the category.

Example:

user1   CategoryA 10
user2   CategoryA 11
user3   CategoryA 9
user4   CategoryB 3
user1   CategoryB 11

the query would return:

Rank  User   Category  
1     user2   CategoryA
2     user1   CategoryA
3     user3   CategoryA
1     user1   CategoryB
2     user4   CategoryB

Any ideas?

I write the query and specify the Category, It works but then I have to write loops and its very slow.

Solution 1

Use "Partition by" in the ranking function OVER clause

SELECT
    Rank() over (Partition by Category Order by Value, User, Category) as ranks,
    Category, User
FROM 
    Table1
Group By
    User, Category, Value 
Order by
    ranks asc

Solution 2

 Select User, Category,
     (Select Count(*) From Table 
      Where Category = A.Category 
         And Value <= A.Value) Rank
 From Table A
 Order By Category, Value

If Value can have duplicates, then you must decide whether you want to 'count' the dupes (equivilent to RANK) or not (equivilent to DENSE_RANK, thanx @shannon)

Ordinary Rank:

 Select User, Category,
     (Select 1 + Count(*) From Table -- "1 +" gives 1-based rank, 
      Where Category = A.Category    -- take it out to get 0-based rank
         And Value < A.Value) Rank
 From Table A
 Order By Category, Value 

"Dense" Rank:

 Select User, Category,
     (Select 1 + Count(Distinct Value) -- "1 +" gives 1-based rank, 
      From Table                       -- take it out to get 0-based rank
      Where Category = A.Category    
         And Value < A.Value) Rank
 From Table A
 Order By Category, Value

Comments

[ZygD]

Very inefficient. The fact he's using RANK implies SQL 2005 at least.

[bladefist]

True. SQL 2008. I'll try all answers

[Charles Bretana]

But a) clarity comes first, then efficiency... and b) problem is about users, so we are not talking billions of records...

[Booji Boy]

shouldn't it be Select User, Category, (Select Count() From Table Where Category = A.Category And Value <= A.Value) Rank From Table A Order By Category ASC, (Select Count() From Table Where Category = A.Category And Value <= A.Value) DESC

[Shannon Severance]

I find the solution with rank function and partition by clearer. You also get different ranks in the case of ties, versus the built in rank function. For example values of 10, 20, 20 will result in 1, 3 3 for your code versus 1, 2, 2 for built in rank.

[Charles Bretana]

@Booji Boy: no, an order by in outer query doesn't matter to the inner subquery rank calculation... @Shannon, yes, so this depends on intent... If you get a 90 on a test where 10 others scored 100, is your rank 2nd or 11th ? Either can be coded using raw SQL. I'm not familiar with SQL 2k5/2k8 Rank function as yet... Can it do both ?

[Shannon Severance]

@Charles. RANK gives 11. DENSE_RANK gives 2. HOWEVER, that is different from what I pointed out. For a row, you are counting the rows ahead, yourself (just like rank) and other rows that tie with yourself. (Unlike rank.) So say 10 100s, and 2 90s. RANK & DENSE_RANK same, but the above gives 12 as the rank.

[Charles Bretana]

@shannon, in the case where column being "ranked" can have duplicates, you must do a count(Distinct RankColumn) instead of Count(*), and then use < or <= (as appropriate) to get 0-based or 1-based rank...

[Shmil The Cat]

I've found the ordinary rank method very useful when working under HyperSQL which to my regret doesn't support yet the PARTITION BY clause under ROW_NUMBER() OVER() , so indeed quadratic performance but when you have no decent windowing function what you can do :)