in a database, you can a column of a table going through phpmyadmin :
- Expand the tree of your database (ocsweb for ex.),
- Choose the table concerned, click on columns,
- Below the list of columns, you can add a column "at the end of the table", "at the beginning of the table" or "after the ID ..."
CAUTION : Proceed carefully, this action is sensitive !
Tip : Before creating a new column, please note the structure of an already existing identical column (type, collation, attributes, null, default, etc.)
Otherwise, you can also add an administrative data in OCS interface, this will create a new column (fields_x) in the accountinfo table of the database (safe method).