DEFAULT

Syntax:
DEFAULT(col_name)

Returns the default value for a table column. An error results if the
column has no default value.

The use of DEFAULT(col_name) to specify the default value for a named
column is permitted only for columns that have a literal default value,
not for columns that have an expression default value.

URL: https://dev.mysql.com/doc/refman/8.0/en/miscellaneous-functions.html