InfoSet Outer Join between two ODS: Sales Line Item and Billing Item

Hi BI/BW experts,

We have a issue with infoSet with left outer join. Currently I have two ODS:

A. Sales Order Line Item ODS

B. Billing Line Item ODS

The A. Sales Item is left outer joined with B. Billing Item by sales order item number and line item number.

Assume that:

A I have Sales Order number 100, 200, and 300.

B Sales order 300, 400.

According to what the concept of the A left outer join B, I should get sales order 100, 200, and 300 related information from sales order ODS and 300 related information from billing ODS. Infact I didn't get any records at all, and the query tell me no records. I found out that even I use left outer join, it actually did inner join.

Any experts have ideas?