DUAL¶

Description

The stored procedure DUAL is a special procedure that only returns one field called dummy of type text. It does not have input parameters and it returns an empty row.

Its main uses are:

• Executing low-cost queries used as ping queries by external clients that access Virtual DataPort via the JDBC and ODBC interfaces.

• Executing VQL functions.

Syntax

Dual()

Privileges Required

No privileges are required to execute this procedure.

Examples

Example 1

SELECT NOW()
FROM DUAL()

This query returns the current time.

The function NOW() is described in the appendix NOW.

Example 2

SELECT 1
FROM DUAL()

This query is a very low-cost query that can be used as ping query by external clients.

Example 3

SELECT 1

This query returns the same as the previous example. That is because the Server assumes that a query that does not have a FROM clause is referencing the Dual() procedure.