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.