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.
No privileges are required to execute this procedure.
SELECT NOW() FROM DUAL()
This query returns the current time.
NOW() is described in the appendix NOW.
SELECT 1 FROM DUAL()
This query is a very low-cost query that can be used as ping query by external clients.
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