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