How to calculate the maximum value of a field expression in result set groups using the MAX() function?

MAX(expr) is a MySQL built-in aggregate function that calculates the maximum value of a field expression in result set groups. For example:

SELECT help_category_id, MAX(help_topic_id), COUNT(help_topic_id)
  FROM mysql.help_topic GROUP BY help_category_id;
  -- +------------------+--------------------+----------------------+
  -- | help_category_id | MAX(help_topic_id) | COUNT(help_topic_id) |
  -- +------------------+--------------------+----------------------+
  -- |                1 |                  1 |                    2 |
  -- |                2 |                 39 |                   35 |
  -- |                3 |                675 |                   59 |
  -- |                4 |                  5 |                    2 |
  -- |                5 |                 44 |                    3 |
  -- ...
  -- +------------------+--------------------+----------------------+

SELECT help_category_id, help_topic_id
  FROM mysql.help_topic WHERE help_category_id = 5;
  -- +------------------+---------------+
  -- | help_category_id | help_topic_id |
  -- +------------------+---------------+
  -- |                5 |            40 |
  -- |                5 |            43 |
  -- |                5 |            44 |
  -- +------------------+---------------+

MAX() is also a window function, you can call it with the OVER clause to calculate the maximum value of the given expression in the current window. For example:

SELECT help_topic_id, help_category_id, 
  MAX(help_topic_id) OVER w
  FROM mysql.help_topic 
  WINDOW w AS (PARTITION BY help_category_id);
  -- +---------------+------------------+---------------------------+
  -- | help_topic_id | help_category_id | MAX(help_topic_id) OVER w |
  -- +---------------+------------------+---------------------------+
  -- |             0 |                1 |                         1 |
  -- |             1 |                1 |                         1 |
  -- |             2 |                2 |                        39 |
  -- |             6 |                2 |                        39 |
  -- |             7 |                2 |                        39 |
  -- |             8 |                2 |                        39 |
  -- |             9 |                2 |                        39 |
  -- ...
  -- +---------------+------------------+---------------------------+

Reference information of the MAX() function:

MAX(expr): max
  Returns the maximum value of expr.

Arguments, return value and availability:
  expr: Required. The field expression in result set groups.
  max: Return value. The maximum value of the input expression.
  Available since MySQL 4.

Related MySQL functions:

• MIN() - Minimum Value in Group
• AVG() - Average Value in Group

⇒ MIN() - Minimum Value in Group

⇐ JSON_OBJECTAGG() - Building JSON Object in Group

⇑ MySQL Functions on Aggregation Groups

⇑⇑ MySQL Function References