About System‑Generated Columns
In some cases of system‑generated columns the DBA specifies the name of the column and whether or not it is to be created for a table and in other cases, the existence, name, and contents of the column are all system‑controlled.
The following system‑generated column types are supported by Teradata Database:
Identity columns are user‑defined, but Teradata Database defines the values inserted into them (in the case of GENERATED ALWAYS AS IDENTITY columns, all column values are system‑generated. In the case of GENERATED BY DEFAULT AS IDENTITY columns, inserted column values can be user‑generated or system‑generated.).
Similarly, BLOB, CLOB, and XML columns are user‑defined, but Teradata Database defines the OID values (see “Object Identifier Columns” on page 820) that point to them.