information_schema.columns.extra

mysql

type: VARCHAR NULL
8
type: VARCHAR NOT NULL
5.7

mariadb

type: NULL
Note:
Additional information about a column, for example whether the column is an invisible column, or, from MariaDB 10.3.6, WITHOUT SYSTEM VERSIONING if the table is not a system-versioned table. A MySQL and MariaDB extension.
© 2022 MariaDB
5.1-10.8
type: VARCHAR NOT NULL
Note:
Additional information about a column, for example whether the column is an invisible column, or, from MariaDB 10.3.6, WITHOUT SYSTEM VERSIONING if the table is not a system-versioned table. A MySQL and MariaDB extension.
© 2022 MariaDB
10.2-10.7

tidb

type: VARCHAR(30) NULL
Note:
Any additional information of the given column.
© 2022 PingCAP
4-6.1

postgres

cockroachdb

mssql