BW best solution for an "outer join"

Hi all, I'm wondering which is the best solution to do the equivalent of an Outer join in sap BW

>> I'm getting data with 3 field, ID Value Field

ID

Value

Field

A Doss1 Doss A Doss2 Doss A Reason1 Reason A Remark1 Remark A Remark2 Remark A Remark3 Remark B Reason2 Reason B Reason1 Reason B Doss1 Doss B Doss2 Doss B Exempt1 Exempt B Remark2 Remark B Remark3 Remark

Through ABAP, I'm trying to split these data to load it into a cube

ID

Doss

Exempt

Remark

Reason

A Doss1 Remark1 Reason1 A Doss2 Remark1 Reason1 A Doss1 Remark2 Reason1 A Doss2 Remark2 Reason1 A Doss1 Remark3 Reason1 A Doss2 Remark3 Reason1 B Doss1 Exempt1 Remark2 Reason2 B Doss1 Exempt1 Remark2 Reason1 B Doss2 Exempt1 Remark2 Reason2 B Doss2 Exempt1 Remark2 Reason1 B Doss1 Exempt1 Remark3 Reason2 B Doss1 Exempt1 Remark3 Reason1 B Doss2 Exempt1 Remark3 Reason2 B Doss2 Exempt1 Remark3 Reason1

With an expert routine, I managed to get 4 table (one for each field) and now I would like to do an outer join between all these table

Do you have some example ?

Thanks in advance