SAP Message AQQIS_CNTRL021 - &1 cannot be connected to two tables using left-outer join

Diagnosis
The system tried to insert a join or convert a join into a left-outerjoin.
The definition would lead to a join condition that does not supportABAP-SQL at the moment:
The right-hand table would be connected with more than one table acrossa left-outer join.
This is not allowed.

System Response
The change was undone.