DUAL table

It is suitable for use in selecting a pseudo column such as SYSDATE or USER.

I created the DUAL table as an underlying object in the Oracle Data Dictionary.

The name, DUAL, seemed apt for the process of creating a pair of rows from just one.

[2] DUAL is readily available for all authorized users in a SQL database.

Several other databases (including Microsoft SQL Server, MySQL, PostgreSQL, SQLite, and Teradata) enable one to omit the FROM clause entirely if no table is needed.