In addition to the table columns that you define, tables contain columns that Teradata Database generates or derives dynamically.
| Column | Description |
|---|---|
| Identity | A column that was specified with the GENERATED ALWAYS AS IDENTITY or GENERATED BY DEFAULT AS IDENTITY option in the table definition. |
| Object Identifier (OID) | For a table that has LOB columns, OID columns store pointers to subtables that store the actual LOB data. |
| PARTITION | For a table that is defined with a partitioned primary index (PPI), the PARTITION column provides the partition number of the combined partitioning expression associated with a row, where the combined partitioning expression is derived from the partitioning expressions defined for each level of the PPI. This is zero for a table that does not have a PPI. |
| PARTITION#L1 through PARTITION#L62 | For tables that are defined with a multilevel PPI, these columns provide the partition number associated with the corresponding level. These are zero for a table that does not have a PPI and zero if the level is greater than the number of partitions. |
| ROWID | Contains the row identifier value that uniquely identifies the row. |
Restrictions apply to using the system-derived and system-generated columns in SQL statements. For example, you can use the keywords PARTITION and PARTITION#L1 through PARTITION#L15 in a query where a table column can be referenced, but you can only use the keyword ROWID in a CREATE JOIN INDEX statement.