It is possible to use aggregate functions as window functions. An aggregate
function used as a window function must have the OVER clause. For example,
here's COUNT() used as a window function:

select COUNT(*) over  (order by column) from table;

MariaDB currently allows these aggregate functions to be used as window
functions:

* AVG
* BIT_AND
* BIT_OR
* BIT_XOR
* COUNT
* JSON_ARRAYAGG
* JSON_OBJECTAGG
* MAX
* MIN
* STD
* STDDEV
* STDDEV_POP
* STDDEV_SAMP
* SUM
* VAR_POP
* VAR_SAMP
* VARIANCE

URL: https://mariadb.com/kb/en/aggregate-functions-as-window-functions/