ZF-7807: Zend_Db_Adapter_Pdo: oci : function describeTable
The left join from all_cons_columns to all_constraints does not include the owner.
This creates a cartesian product if there are more than one identical db-schemes installed in one Database (i.e. two different test schemes in one Database).
It may also give wrong results, if the constraint does exist in one scheme and is missing in the other.