如何獲取多列之間的2個最大值？

Question

我想弄清楚如何從5個字段中獲得2個最高值。我知道greatest函數，但我不知道如何提取第二高的值。

基本上，該表有5個NUMBER類型字段。在這個例子中，最後兩列是我想要的結果。

| Score1 | Score2 | Score3 | Score4 | Score5 | | Highest1_value | Highest2_value 
+--------+--------+--------+--------+--------+ +----------------+--------------- 
| 10 | 20 | 30 | 40 | 50 | |  50  |  40 
| 20 | 20 | 12 | 17 | 0 | |  20  |  20 
|  7 |  7 |  7 |  7 | 11.1 | |  11.1  |  7 
| 10 | 10 | 10 | 10 | 10 | |  10  |  10 

Answer 1

不透視數據並使用row_number獲得每個ID的前2個最高分數。

select id 
,max(case when rnum=1 then val end) as highest_1 
,max(case when rnum=2 then val end) as highest_2 
from (select id,score,val,row_number() over(partition by id order by val desc) as rnum 
     from (select * from t --replace this with your tablename 
      unpivot (val for score in (score1,score2,score3,score4,score5)) p 
     ) tbl 
    ) tbl 
group by id 

Answer 2

如果我正確理解，你需要這樣的：

select your_table.*, REGEXP_SUBSTR(h.str, '^[^\-]+') AS h1, REGEXP_SUBSTR(h.str, '[^\-]+$') AS h2 FROM your_table 
inner join (
    select id, listagg(sc, '-') WITHIN GROUP (ORDER BY sc DESC) str FROM(
     select id, sc, row_number() over(partition by id order by sc desc) rn from (
      select id, sc FROM your_table 
      UNPIVOT (sc for col in (Score1, Score2, Score3, Score4, Score5)) 
     ) tt 
    )ttt 
    where rn <= 2 
    GROUP BY id 
) h 
ON your_table.id = h.id 

Answer 3

該解決方案避免了unpivot，只是很多切&粘貼&修改：基於@ VKP的&

SELECT 
    dt.*, 
    CASE maxscore -- GREATEST on all but the highest value, 
       -- simplified to a "Valued Case" based on mathguy's comment 
     WHEN score1 THEN Greatest(score2, score3, score4, score5) 
     WHEN score2 THEN Greatest(score1, score3, score4, score5) 
     WHEN score3 THEN Greatest(score1, score2, score4, score5) 
     WHEN score4 THEN Greatest(score1, score2, score3, score5) 
     ELSE Greatest(score1, score2, score3, score4) 
    END 
FROM 
(
    SELECT t.*, 
     Greatest(Score1,Score2,Score3,Score4,Score5) AS maxscore 
    FROM tab t 
) dt 

@ mathguy的評論沒有Derived Table/Inline View：

SELECT 
    t.*, 
    Greatest(Score1,Score2,Score3,Score4,Score5) as Highest1_value, 
    CASE Greatest(Score1,Score2,Score3,Score4,Score5)-- GREATEST on all but the highest value 
     WHEN score1 THEN Greatest(  score2,score3,score4,score5) 
     WHEN score2 THEN Greatest(score1,  score3,score4,score5) 
     WHEN score3 THEN Greatest(score1,score2,  score4,score5) 
     WHEN score4 THEN Greatest(score1,score2,score3,  score5) 
     ELSE    Greatest(  score1,score2,score3,score4) 
    END as Highest2_value 
FROM tab t