数据：

一、整体排名（3种）

-- 普通排名：从1开始，顺序往下排

set @rank =0;
select city ,score, @rank := @rank+1 rank 
 from cs order by score desc;

-- 并列排名：相同的值是相同的排名,不用占空位

set @rank=0,@price=null;
select cs.* ,
 case when @price = score then @rank 
 when @price := score then @rank := @rank+1 end rank  
 from cs order by score desc;
 -- 当查询的score 值 = @price时，输出@rank,
 -- 当不等时，将score值赋给@price ，并输出@rank := @rank+1

-- 或者
set @rank=0,@price=null;
select a.city,a.score,a.rank from 
(select cs.*,
@rank := if(@p=score,@rank,@rank+1) rank,
@p := score
from cs order by score desc) a;

-- 并列排名：相同的值是相同的排名,需要占空位

set @rank=0,@price=null, @z=1;
select a.city,a.score,a.rank from 
(select cs.*,
@rank := if(@p=score,@rank,@z) rank,
@p := score,@z :=@z+1
from cs order by score desc) a;

二、分组后组内排名（3种）

-- 分组普通排名：顺序排名

set @rank=0,@c=null;
select cs.city,cs.score,
@rank := if(@c = city,@rank+1,1) rank,
@c := city
from cs order by cs.city,cs.score;

-- 组内并列排名：相同的值是相同的排名,不需要占空位

set @rank=0,@c=null,@s=null;
select cs.city,cs.score,
@rank := if(@c=city,if(@s=score,@rank,@rank+1),1) rank ,
@c := city,@s :=score 
from cs order by cs.city,cs.score;

-- 组内并列排名：相同的值是相同的排名,需要占空位

set @rank=0,@z=0,@c=null,@s=null;
select cs.city,cs.score,
@z := if(@c=city,@z+1,1),
@rank := if(@c=city,if(@s=score,@rank,@z),1) rank,
@c := city,@s :=score 
from cs order by cs.city,cs.score;

三、分组后取各组的前两名

-- 方法1：按照分组排名的三种方式，然后限定排名的值

set @rank=0,@z=0,@c=null,@s=null;
select a.city,a.score,a.rank from 
(select cs.city city,cs.score score,
@z := if(@c=city,@z+1,1),
@rank := if(@c=city,if(@s=score,@rank,@z),1) rank,
@c := city,@s :=score 
from cs order by cs.city,cs.score desc) a
where a.rank<=2;

-- 方法2：内部查询

SELECT * FROM cs c
WHERE (
    SELECT count(*) FROM cs
    WHERE c.city=cs.city AND c.score<cs.score )<2
  ORDER BY city,score DESC;