Php 三列-使用SQL获取最大值

我有一张桌子：

评级：

id | one | two | three
1  | 12  | 3   | 7
2  | 11  | 30  | 3
3  | 8   | 14  | 4

如何从这些字段（1、2、3）中获取SQL最大值？对于本例，这是30

您可以取消打印类似以下内容的数据：

select max(value)
from
(
  select id, 'one' col, one value
  from yourtable
  union all
  select id, 'two' col, two value
  from yourtable
  union all
  select id, 'three' col, three value
  from yourtable
) src

看

或者您可以使用类似以下内容：

SELECT max(data)
FROM 
(
  SELECT 
    CASE s.col
      WHEN 'one' THEN one
      WHEN 'two' THEN two
      WHEN 'three' THEN three
    END AS DATA
  FROM yourtable t
  CROSS JOIN 
  (
    SELECT 'one' AS col
    UNION ALL SELECT 'two'
    UNION ALL SELECT 'three'
  ) s
) s

请参见MySQL中的

，您可以使用以下功能：

SELECT  MAX(GREATEST(one, two, three))
FROM    T;

尝试此查询

SELECT tempTable.id, tempTable.max(val) 
FROM (SELECT id, max(one) AS val
      FROM tbl 
      UNION 
      SELECT id, max(two) AS val
      FROM tbl 
      UNION 
      SELECT id, max(three) AS val
      FROM tbl
) AS tempTable;

---

您可以使用

case

语句

SELECT
    CASE
        WHEN one >= two AND one >= three THEN one
        WHEN two >= one AND two >= three THEN two
        WHEN three >= one AND three >= two THEN three
        ELSE one
    END AS MaxVal

Oracle中还存在“最大”功能，因此此解决方案也适用于Oracle。

SELECT MAX(field) FROM (
    SELECT one AS field FROM table
    UNION 
    SELECT two AS field FROM table
    UNION 
    SELECT three AS field FROM table
) AS t

select GREATEST(max(one), max(two), max(three)) as maximum 
from table;

SELECT
    CASE
        WHEN one >= two AND one >= three THEN one
        WHEN two >= one AND two >= three THEN two
        WHEN three >= one AND three >= two THEN three
        ELSE one
    END AS MaxVal