Getting data without using joins from database

HI,

I have almost 4 table in use which is ekko, ekkn,rseg, ekpo, from this get I differents fields according to my requirement by using of purchasing document no and joins, which is common field in all of 4 tables,I have made a structure in my code, which like :

tables:begin of purchase_order

ebeln like ekko-ebeln,

neptr like ekkn-neptr,

belnr like rseg-belnr,

--- like ekpo-

-

-

-

-

-

-

end of purchase_order.

itb type purchase_order,

wtb like table of itb,

and get data by making joins on these 3 tables like:

Select a~ebeln ...... b~neptr........ c~belnr into corresponding fields of wtb from ekko as a inner join ekkn as b on b~ebeln = a~ebeln inner join rseg as c on

c~eblen = a~ebeln,-------------------------------------- where a~ebeln = ebeln-ekko,

Well this code works fine but now my problem is that my supervisor told me to do this work by without using joins,, by using loop at itb or like that, I have googled it to find the solution or answer , spent hell of my time in net searching but couldn't fine satisfactory solution, please help me to find the solution to solve this problem as I am newbie in sap abap.