SQL 根据每行中的值对列进行排名

Question

我有一个 SQL table 看起来类似于下面的示例。

对于每一行，我想添加 4 列来表示每个主题的排名（对于给定的行）。

是否可以在 SQL 内完成？请帮忙。我使用 Vertica SQL.

Answer 1

一种方法是取消数据透视并重新聚合：

select name, 
       max(case when seqnum = 1 then subject end) as rank_1,
       max(case when seqnum = 2 then subject end) as rank_2,
       max(case when seqnum = 3 then subject end) as rank_3,
       max(case when seqnum = 4 then subject end) as rank_4
from (select s.*,
             row_number() over (partition by name order by score desc) as seqnum      
      from ((select name, 'English' as subject, english as score from t) union all
            (select name, 'Maths', maths from t) union all
            (select name, 'Science', science from t) union all
            (select name, 'Physics', Physics from t)
           ) s
     ) s
group by name;

这是一个数据库<>fiddle。

Answer 2

稍微复杂一点；至少，在我看来。

分解成几个子查询

WITH
-- your input - *please* paste it as text into your question next time - 
-- I had to re-type all of that instead of just reformatting it ...
-- and I use "nam" instead of "name", as it's a reserved word ...
indata(nam,english,science,physics,maths) AS (
            SELECT 'A',80,72,53,86
  UNION ALL SELECT 'B',60,65,75,52
  UNION ALL SELECT 'C',79,77,44,70
  UNION ALL SELECT 'D',69,69,55,65
)
,
-- add an in-line table with all subjects, to un-pivot with ...
subjects(subject) AS (
            SELECT 'english'
  UNION ALL SELECT 'science'
  UNION ALL SELECT 'physics'
  UNION ALL SELECT 'maths'
)
,
-- un-pivot, by CROSS JOINing and 
-- get a rank, based on combination of 
-- nam and the right mark based on subject ..
piv AS (
  SELECT
    *
  , ROW_NUMBER() OVER(
      PARTITION BY nam
      ORDER BY 
        CASE subject
          WHEN 'english' THEN english
          WHEN 'science' THEN science
          WHEN 'physics' THEN physics
          WHEN 'maths'   THEN maths
          ELSE 0
        END 
      DESC
    ) AS rnk
  FROM indata CROSS JOIN subjects
)
-- control query ....
-- SELECT * FROM piv ORDER BY nam,rnk;
-- out  nam | english | science | physics | maths | subject | rnk 
-- out -----+---------+---------+---------+-------+---------+-----
-- out  A   |      80 |      72 |      53 |    86 | maths   |   1
-- out  A   |      80 |      72 |      53 |    86 | english |   2
-- out  A   |      80 |      72 |      53 |    86 | science |   3
-- out  A   |      80 |      72 |      53 |    86 | physics |   4
-- out  B   |      60 |      65 |      75 |    52 | physics |   1
-- out  B   |      60 |      65 |      75 |    52 | science |   2
-- out  B   |      60 |      65 |      75 |    52 | english |   3
-- out  B   |      60 |      65 |      75 |    52 | maths   |   4
-- out  C   |      79 |      77 |      44 |    70 | english |   1
-- out  C   |      79 |      77 |      44 |    70 | science |   2
-- out  C   |      79 |      77 |      44 |    70 | maths   |   3
-- out  C   |      79 |      77 |      44 |    70 | physics |   4
-- out  D   |      69 |      69 |      55 |    65 | english |   1
-- out  D   |      69 |      69 |      55 |    65 | science |   2
-- out  D   |      69 |      69 |      55 |    65 | maths   |   3
-- out  D   |      69 |      69 |      55 |    65 | physics |   4

-- finally, re-pivot, by GROUP-ing by the original columns of "indata"
-- and applying a MAX(CASE ...) to the columns I want to add.
SELECT
  nam
, english
, science
, physics
, maths
, MAX(CASE rnk WHEN 1 THEN subject END) AS rank_1
, MAX(CASE rnk WHEN 2 THEN subject END) AS rank_2
, MAX(CASE rnk WHEN 3 THEN subject END) AS rank_3
, MAX(CASE rnk WHEN 4 THEN subject END) AS rank_4
FROM piv
GROUP BY
  nam
, english
, science
, physics
, maths
ORDER BY nam;
-- out  nam | english | science | physics | maths | rank_1  | rank_2  | rank_3  | rank_4  
-- out -----+---------+---------+---------+-------+---------+---------+---------+---------
-- out  A   |      80 |      72 |      53 |    86 | maths   | english | science | physics
-- out  B   |      60 |      65 |      75 |    52 | physics | science | english | maths
-- out  C   |      79 |      77 |      44 |    70 | english | science | maths   | physics
-- out  D   |      69 |      69 |      55 |    65 | english | science | maths   | physics

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