Simple filtering by a single criterion

The GetErrors query, from the MultiLogApp sample application, filters the log file data in Log4ErrorWarningStream to pass only error messages to ErrorStream:

CREATE CQ GetErrors 
INSERT INTO ErrorStream 
SELECT log4j 
FROM Log4ErrorWarningStream log4j WHERE log4j.level = 'ERROR';

Messages with any other error level (such as WARN or INFO) are discarded.