Pseudo Columns

A pseudocolumn behaves like a table column, but is not actually stored in the table. You can select from pseudocolumns, but you cannot insert, update, or delete their values. A pseudocolumn is also similar to a function without arguments. However, functions without arguments typically return the same value for every row in the result set, whereas pseudocolumns typically return a different value for each row.

The OLAP expression syntax supports these pseudo columns.

Descriptions of Pseudo Columns
Pseudo Column	Return Value	Description
`CURRENT_DATE`	`DATE`	The current date in the session time zone.
`DBTIMEZONE`	`VARCHAR2`	The value of the database time zone as either a time zone offset from Coordinated Universal Time (UTC) or a time zone region name.
`SESSIONTIMEZONE`	`VARCHAR2`	The time zone of the current session.
`SYSDATE`	`DATE`	The current date and time of the operating system on which the database resides. The format of the value depends on the value of the `NLS_DATE_FORMAT` initialization parameter.
`SYSTIMESTAMP`	`TIMESTAMP WITH TIME ZONE`	The system date, including fractional seconds and time zone, of the system on which the database resides.
`UID`	`NUMBER`	An integer that uniquely identifies the session user.
`USER`	`VARCHAR2`	The user name of the current user.