InfoSet Join condition

Hi gurus!

We have an InfoSet joining 2 ODS's bye bill number and position. It's a simple join whitout any filter or condition but when we check data there are records missing. If we look at the SQL query there is a where clause and we don´t know why. Here you have the SQL:

select

N'0000' AS , .[BILL_NUM] AS , .[BILL_ITEM] AS , COUNT( * ) AS

FROM

JOIN

ON

.[BATCH] = .[AU_VHCLE]

AND ( ( ( ( ( ( (.[AU_DYIS] IS NULL ) ) OR ( ( .[AU_DYIS]= N'0000' ) ) ) ) ) )

)

GROUP BY

.[AU_DYIS],[T00002].[BILL_NUM],[T00002].[BILL_ITEM]

ORDER BY

ASC, ASC, ASC

what is AU_DYIS doing there??? we have never done anything with AU_DYIS on the IS definition!!

Thanks guys!