来自两个或多个领域的最大价值 [英] Biggest value from two or more fields

问题描述

我需要从两个领域中获得最大价值:

I need to get the biggest value from two fields:

SELECT MAX(field1), MAX(field2)

现在，我怎么能从这两个中获得最大的价值?

Now, how can I get biggest value from these two?

推荐答案

您可能要使用

You may want to use the GREATEST() function:

SELECT GREATEST(field1, field2);

如果要从所有行中获取绝对最大值，则可能需要使用以下内容:

If you want to get the absolute maximum from all the rows, then you may want to use the following:

SELECT GREATEST(MAX(field1), MAX(field2));

示例1:

SELECT GREATEST(1, 2);
+----------------+
| GREATEST(1, 2) |
+----------------+
|              2 |
+----------------+
1 row in set (0.00 sec)

示例2:

CREATE TABLE a (a int, b int);

INSERT INTO a VALUES (1, 1);
INSERT INTO a VALUES (2, 1);
INSERT INTO a VALUES (3, 1);
INSERT INTO a VALUES (1, 2);
INSERT INTO a VALUES (1, 4);

SELECT GREATEST(MAX(a), MAX(b)) FROM a;
+--------------------------+
| GREATEST(MAX(a), MAX(b)) |
+--------------------------+
|                        4 |
+--------------------------+
1 row in set (0.02 sec)

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