create table assets (

  item_name varchar(32) primary key, -- A common attribute for all items

  dynamic_cols  blob  -- Dynamic columns will be stored here

);

INSERT INTO assets VALUES 

  ('MariaDB T-shirt', COLUMN_CREATE('color', 'blue', 'size', 'XL'));

INSERT INTO assets VALUES

  ('Thinkpad Laptop', COLUMN_CREATE('color', 'black', 'price', 500));

alter table assets add column color char(32) as (left(COLUMN_GET(dynamic_cols, 'color' as char),32)) persistent;

mysql 10.0.10-MariaDB (root) [test]> alter table assets add column color char(32) as (left(COLUMN_GET(dynamic_cols, 'color' as char),32)) persistent;

Query OK, 2 rows affected, 2 warnings (0.03 sec)

Records: 2  Duplicates: 0  Warnings: 2

mysql 10.0.10-MariaDB (root) [test]> show warnings;

+---------+------+--------------------------------------------+

| Level   | Code | Message                                    |

+---------+------+--------------------------------------------+

| Warning | 1265 | Data truncated for column 'color' at row 1 |

| Warning | 1265 | Data truncated for column 'color' at row 2 |

+---------+------+--------------------------------------------+

2 rows in set (0.00 sec)

mysql 10.0.10-MariaDB (root) [test]> show create table assets\G

*************************** 1. row ***************************

       Table: assets

Create Table: CREATE TABLE `assets` (

  `item_name` varchar(32) NOT NULL,

  `dynamic_cols` blob,

  `color` char(0) AS (left(COLUMN_GET(dynamic_cols, 'color' as char),32)) PERSISTENT,

  PRIMARY KEY (`item_name`)

) ENGINE=InnoDB DEFAULT CHARSET=latin1

1 row in set (0.00 sec)