WQL Generic Failure - JOIN Statement

Question

I'm trying to execute the following query through wbemtest, and it's failing.
select * from sms_program join sms_package on sms_package.packageid = sms_program.packageid
However, a very similar query, just using two different tables (WMI classes), works just fine:
select * from sms_r_system join sms_g_system_operating_system on sms_r_system.ResourceID = sms_g_system_operating_system.ResourceID
I'm getting a "generic failure" when I try to run the former query. Any ideas?
Thanks,
Trevor Sullivan
Systems Engineer
OfficeMax Corporation.

Answer 1

Try to avoid
select * from class_A join class-B on class_A.id = class_B.id
It is asking for bad performance in your code. the WQL query will return __Generic object and with each instance returned there will addtional overhead for the schema for the instance.
If possible, use join only to limit the rows returned, but still return properties from only one class
select class_A.* from class_A join class-B on class_A.id = class_B.id
If you have to return properties from multiple classes and want to handle the __Generic object, try to be specific what properties you are trying to get.
This issue you are hitting is that: there a limit on how much data one instance can return per WQL query. You will not hit the issue if you choose to do the following
select sms_program.* from sms_program join sms_package on sms_package.packageid = sms_program.packageid
or
select sms_program.programname, sms_program.packageid, sms_package.name from sms_program join sms_package on sms_package.packageid = sms_program.packageid