The Dynamic columns feature was introduced in MariaDB 5.3.
 
Syntax
------ 
COLUMN_ADD(dyncol_blob, column_nr, value [as type],
[column_nr, value [as type]]...);
COLUMN_ADD(dyncol_blob, column_name, value [as type],
[column_name, value [as type]]...);
 
Description
----------- 
Adds or updates dynamic columns.
dyncol_blob must be either a valid dynamic columns blob (for
example, COLUMN_CREATE returns such blob), or an empty
string.
column_name specifies the name of the column to be added. If
dyncol_blob already has a column with this name, it will be
overwritten.
value specifies the new value for the column. Passing a NULL
value will cause the column to be deleted.
as type is optional. See #datatypes section for a discussion
about types.
 
The return value is a dynamic column blob after the
modifications.
 
Examples
-------- 
-- MariaDB 5.3+:
UPDATE tbl SET dyncol_blob=COLUMN_ADD(dyncol_blob, 1
/*column id*/, "value") WHERE id=1;
 
-- MariaDB 10.0.1+:
UPDATE t1 SET dyncol_blob=COLUMN_ADD(dyncol_blob,
"column_name", "value") WHERE id=1;
 
Note: COLUMN_ADD() is a regular function (just like
CONCAT()), hence, in order to update the value in the table
you have to use the UPDATE ... SET
dynamic_col=COLUMN_ADD(dynamic_col,
....)  pattern.
 

 
 
 
 
 
 
 

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