You can perform basic filtering on a stream using the SQL WHERE clause. Given a stream with web login event data, the following query selects only those for which the login was unsuccessful:
SELECT STREAM *
FROM "WebAppLoginEvents"
WHERE "loginSuccessful" = FALSE;
Streams can be combined using the SQL UNION ALL operator. The resulting output stream simply consists of all rows from both the input streams. For example, the following query produces a stream of orders taken over the phone or via the web:
SELECT STREAM *
FROM PhoneOrders
UNION ALL
SELECT STREAM *
FROM WebOrders