MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0
ALTER FUNCTIONfunc_name[characteristic...]characteristic: { COMMENT 'string' | LANGUAGE SQL | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA } | SQL SECURITY { DEFINER | INVOKER } }
      This statement can be used to change the characteristics of a
      stored function. More than one change may be specified in an
      ALTER FUNCTION statement. However,
      you cannot change the parameters or body of a stored function
      using this statement; to make such changes, you must drop and
      re-create the function using DROP
      FUNCTION and CREATE
      FUNCTION.
    
      You must have the ALTER ROUTINE
      privilege for the function. (That privilege is granted
      automatically to the function creator.) If binary logging is
      enabled, the ALTER FUNCTION
      statement might also require the
      SUPER privilege, as described in
      Section 27.7, “Stored Program Binary Logging”.