CODEWITHSUNDEEP
mysqlsqlsortingrankingmysql-variables
Anar Bayramov
Anar Bayramov

Reputation: 11584

Rank users in mysql by their points

I am trying to rank my students by their points that I've calculated before but the problem is if students have same points they both should be in same rank E.g

Student 1 has full points Student 2 has full points

they both have to be rank as 1;

enter image description here Here an example of my database

the query I am trying to do is (just for select then I can insert the values to my column) 

 SELECT  a.points
        count(b.points)+1 as rank
FROM  examresults a left join examresults b on a.points>b.points
group by  a.points;

Edit for being more clear:

their ranks should be like

my current query returns a values like

enter image description here

As it is missing the third rank. (because second rank has 2 values)

Upvotes: 3

Views: 1967

Answers (3)

Juan Carlos Oropeza
Juan Carlos Oropeza

Reputation: 48197

This is just a fix of Gordon solution using variables. The thing is your rank function isnt the way rank should work. (student 4 should be rank 4)

SQL Fiddle Demo You can add more student to improve the testing.

select er.*,
       (@rank := if(@points = points, 
                    @rank, 
                    if(@points := points,    
                       @rank + 1, 
                       @rank + 1                       
                      )
                   )                  
       ) as ranking
from students er cross join
     (select @rank := 0, @points := -1) params
order by points desc;

OUTPUT

| id | points | ranking |
|----|--------|---------|
|  1 |     80 |       1 |
|  2 |     78 |       2 |
|  3 |     78 |       2 |
|  4 |     77 |       3 |
|  5 |     66 |       4 |
|  6 |     66 |       4 |
|  7 |     66 |       4 |
|  8 |     15 |       5 |

Upvotes: 2

Gouda Elalfy
Gouda Elalfy

Reputation: 7023

this query achieve what do you want:

SELECT  student_id , points, (select count(distinct(points))+1 as rank 
from examresults internal 
where internal.points > external.points order by points)
FROM  examresults external 
group by  student_id

Upvotes: 0

Gordon Linoff
Gordon Linoff

Reputation: 1269743

You want a real rank, which is calculated by the ANSI standard rank() function. You can implement this in MySQL using this logic:

select er.*,
       (select 1 + count(*)
        from examresults er2
        where er2.points > er.points
       ) as ranking
from exampleresults er;

For larger tables, you can do this with variables, but it is a rather awkward:

select er.*,
       (@rank := if(@rn := @rn + 1              -- increment row number
                    if(@points = points, @rank, -- do not increment rank
                       if(@points := points,    -- set @points
                          @rn, @rn              -- otherwise use row number
                         )
                       )
                   )
       ) as ranking
from examresults er cross join
     (select @rn := 0, @rank := 0, @points := -1) params
order by points desc;

Upvotes: 1

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