Syntax
------

MAX([DISTINCT] expr)

Description
-----------

Returns the largest, or maximum, value of expr. MAX() can also take a string
argument in which case it returns the maximum string value. The DISTINCT
keyword can be used to find the maximum of the distinct values of expr,
however, this produces the same result as omitting DISTINCT.

Note that SET and ENUM fields are currently compared by their string value
rather than their relative position in the set, so MAX() may produce a
different highest result than ORDER BY DESC.

It is an aggregate function, and so can be used with the GROUP BY clause.

MAX() can be used as a window function.

MAX() returns NULL if there were no matching rows.

Examples
--------

CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT);

INSERT INTO student VALUES 
 ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
 ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
 ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
 ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);

SELECT name, MAX(score) FROM student GROUP BY name;
+---------+------------+
| name    | MAX(score) |
+---------+------------+
| Chun    |         75 |
| Esben   |         43 |
| Kaolin  |         88 |
| Tatiana |         87 |
+---------+------------+

MAX string:

SELECT MAX(name) FROM student;
+-----------+
| MAX(name) |
+-----------+
| Tatiana   |
+-----------+

Be careful to avoid this common mistake, not grouping correctly and returning
mismatched data:

SELECT name,test,MAX(SCORE) FROM student;
+------+------+------------+
| name | test | MAX(SCORE) |
+------+------+------------+
| Chun | SQL  |         88 |
+------+------+------------+

Difference between ORDER BY DESC and MAX():

CREATE TABLE student2(name CHAR(10),grade ENUM('b','c','a'));

INSERT INTO student2 VALUES('Chun','b'),('Esben','c'),('Kaolin','a');

SELECT MAX(grade) FROM student2;
+------------+
| MAX(grade) |
+------------+
| c          |
+------------+

SELECT grade FROM student2 ORDER BY grade DESC LIMIT 1;
+-------+
| grade |
+-------+
| a     |
+-------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score
TINYINT);
INSERT INTO student_test VALUES 
  ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
  ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
  ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
  ('Tatiana', 'SQL', 87);

SELECT name, test, score, MAX(score) 
 OVER (PARTITION BY name) AS highest_score FROM student_test;
+---------+--------+-------+---------------+
| name    | test   | score | highest_score |
+---------+--------+-------+---------------+
| Chun    | SQL    |    75 |            75 |
| Chun    | Tuning |    73 |            75 |
| Esben   | SQL    |    43 |            43 |
| Esben   | Tuning |    31 |            43 |
| Kaolin  | SQL    |    56 |            88 |
| Kaolin  | Tuning |    88 |            88 |
| Tatiana | SQL    |    87 |            87 |
+---------+--------+-------+---------------+

URL: https://mariadb.com/kb/en/max/