Syntax:
MIN([DISTINCT] expr)

Returns the minimum value of expr. MIN() may take a string argument; in
such cases, it returns the minimum string value.
The DISTINCT keyword can be used to find the minimum of the distinct values
of expr, however, this produces the same result as omitting DISTINCT.

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

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

