Question

我有一张如下表格

ID     M1    M2    M3   M4  M5
121    3      5     6    8   4
122    5      2     1    9   6

对于每一行，我需要获得具有最大值的三列，其他值应为NULL。对于上表，输出应为：

ID     M1    M2    M3   M4  M5
121          5     6    8   
122    5                9   6

任何人都可以帮我在Oracle或MySQL中如何做到这一点吗？

Answer 1

如果您想从表中获取最大值，可以使用以下子查询：

SELECT ID
,(CASE WHEN M1 = MM1 THEN M1 ELSE '' END) AS M1
,(CASE WHEN M2 = MM2 THEN M2 ELSE '' END) AS M2
,(CASE WHEN M3 = MM3 THEN M3 ELSE '' END) AS M3
,(CASE WHEN M4 = MM4 THEN M4 ELSE '' END) AS M4
,(CASE WHEN M5 = MM5 THEN M5 ELSE '' END) AS M5
FROM Table1
JOIN
(
SELECT MAX(M1) AS MM1
      ,MAX(M2) AS MM2
      ,MAX(M3) AS MM3
      ,MAX(M4) AS MM4
      ,MAX(M5) AS MM5
FROM Table1
) A

输出：

|  ID | M1 | M2 | M3 | M4 | M5 |
--------------------------------
| 121 |    |  5 |  6 |    |    |
| 122 |  5 |    |    |  9 |  6 |

See this SQLFiddle

Answer 2

试试这个（aaabbb是我在小提琴中给你的桌子的名字）：

with p as (
select *
from aaabbb
unpivot
(
v for c in (m1,m2,m3,m4,m5)
)
), max_v as (
select p1.id,  max(p1.v) v1, max(p2.v) v2, max(p3.v) v3
from p p1 
join p p2 on p1.v > p2.v and  p1.id = p2.id
join p p3 on p2.v > p3.v and  p2.id = p3.id
group by p1.id) 
select ab.id, 
case when m1 in (mv.v1, mv.v2, mv.v3) then m1 end  m1,
case when m2 in (mv.v1, mv.v2, mv.v3) then m2 end  m2,
case when m3 in (mv.v1, mv.v2, mv.v3) then m3 end  m3,
case when m4 in (mv.v1, mv.v2, mv.v3) then m4 end  m4,
case when m5 in (mv.v1, mv.v2, mv.v3) then m5 end  m5
from aaabbb ab join max_v mv on ab.id = mv.id

结果是：

ID     M1    M2    M3   M4  M5
121          5     6    8   
122    5                9   6

Here是一个sqlfiddle演示

Answer 3

在oracle :: 我不确定你试图在这里调用的某个规则：

select id,
decode(m1,1,null,2,null,3,null,4,null,M1) M1,
decode(m2,1,null,2,null,3,null,4,null,M2) M2,
decode(m3,1,null,2,null,3,null,4,null,M3) M3,
decode(m4,1,null,2,null,3,null,4,null,M4) M4,
decode(m5,1,null,2,null,3,null,4,null,M5) M5
from tab order by id;

Answer 4

尝试此查询 -

SELECT
  id,
  IF(t1.m1 = t2.m1, t1.m1, null) m1,
  IF(t1.m2 = t2.m2, t1.m2, null) m2,
  IF(t1.m3 = t2.m3, t1.m3, null) m3,
  IF(t1.m4 = t2.m4, t1.m4, null) m4,
  IF(t1.m5 = t2.m5, t1.m5, null) m5
FROM
  m_table t1,
  (SELECT
     MAX(m1) m1, MAX(m2) m2, MAX(m3) m3, MAX(m4) m4, MAX(m5) m5 FROM m_table
  ) t2

如何从五列中获得最佳的三列？

4 个答案:

See this SQLFiddle