Using Eclipse datasource explorer with teiid connection using SHOWPLAN to demonstrate the problem.

Enter: SELECT * FROM SECURITY.SYSINFO WHERE SYSID = 'DE29 AND SYSID <> 'DE29'

USER COMMAND appears as: SELECT * FROM SECURITY.SYSINFO WHERE SYSID = 'DE29

Apparently conflicting "AND SYSID <> 'DE29'" is dropped and I get results from SYSID = 'DE29'.

Enter: SELECT * FROM SECURITY.SYSINFO WHERE SYSID <> 'DE29' AND SYSID = 'DE29'

USER COMMAND appears as: SELECT * FROM SECURITY.SYSINFO WHERE 1 = 0

And I get expected null result set.

Admittedly irrational query but it should give empty result set however you order the WHERE clause conditions.