三列 - 用SQL获取MAX

Question

我有桌子:

评分:

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

如何从这些字段(一,二,三)中获取SQL MAX值？对于这个例子,这是30.

Answer 1

在MySQL中,您可以使用GREATEST函数:

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

关于SQL小提琴的例子

Answer 2

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