Difference between revisions of "SQL Pseudo Columns"
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Revision as of 09:16, 16 March 2009
PSEUDO COLUMNS
Class
SQL Applications
Purpose
Provide extra information about a SELECT row set
See Also
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. |
