SQL Pseudo Columns

PSEUDO COLUMNS

Class

SQL Applications

Purpose

Provide extra information about a SELECT row set

See Also

INSERT, SELECT, UPDATE

Description

A Pseudo Column behaves like a table column, but is not actually stored in the table. You can select from Pseudo Columns, but they cannot be updated. They provide extra information about a row set.

Pseudo Columns	Description
CURRVAL	The CURRVAL Pseudo Column will return the current sequence number from the specified table. Sequence numbers can be used for primary and unique index keys.
NEXTVAL	The NEXTVAL Pseudo Column will return the next unique sequence number from the specified table. Sequence numbers can be used for primary and unique index keys.
ROWID	The ROWID Pseudo Column will return a number identifying the row’s physical stored position in the table. The ROWID Pseudo Column can be used to perform singleton selects, or optimize updates of a known ROWID.
ROWNUM	The ROWNUM Pseudo Column will return a number indicating the order in which the rows are selected from the table.
SQLCNT	The SQLCNT Pseudo Column will return the number of rows affected by the last SQL statement. For example, after a SELECT statement, SQLCNT will contain the number of rows selected.
SQLCODE	The SQLCODE Pseudo Column will return a number indicating the result of the last SQL statement.
SYNCNUM	The SYNCNUM pseudo column will return the unique sequence number assigned to a row from the specified table.