DUAL behavior in 10g and prior versions
(Doc ID 728710.1)
Last updated on NOVEMBER 17, 2019
Applies to:Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Backup Service - Version N/A and later
Information in this document applies to any platform.
This problem can occur on any platform.
The SYS-owned dual table was introduced by Oracle long back and since then the Application
Development team across the globe has been using this table for some internal processing.
Some of the common queries on DUAL table used by the application team are :
select sysdate from dual;
select sequence.nextval from dual;
select sys_context('USERENV','SESSION_USER') from dual;
Originally, this table was introduced by Oracle for its internal processing, for example, RMAN
uses this table to fetch the current date for a backup.
Getting multiple rows in DUAL can cause a variety of known issues.
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In this Document