MariaDB [test]> CREATE TABLE steuern (
    -> netto FLOAT NOT NULL,
    -> brutto FLOAT AS (netto*1.19));
Query OK, 0 rows affected (0.10 sec)

MariaDB [test]> INSERT INTO steuern VALUES (100,default);
Query OK, 1 row affected (0.00 sec)

MariaDB [test]> SELECT * FROM steuern;
+--------+-------+
|  netto |brutto |
+--------+-------+
|    100 |   119 |
+--------+-------+
1 row in set (0.00 sec)

MariaDB [test]> DESCRIBE steuern;
+--------+-------+------+-----+---------+---------+
| Field  | Type  | Null | Key | Default | Extra   |
+--------+-------+------+-----+---------+---------+
|  netto | float | NO   |     | NULL    |         |
| brutto | float | YES  |     | NULL    | VIRTUAL |
+--------+-------+------+-----+---------+---------+
2 rows in set (0.01 sec)