Its nothing but Combining the common fields which makes synthetic keys

Ex:

Tab1:

Load

Country,

Region,

Sales,

Products

From --------------;

Tab2:

Load

Country,

Region,

Customer,

Outstanding

From ---------------;

If you load these 2 tables directly your script contains synthetic keys (Country and Region-- common in both tables)

Sol:

Tab1:

Country&'-'&Region as Key    //Composite key

Sales

Products

From --------------;

Tab2:

Country&'-'&Region as Key   //Composite key

Customer,

Outstanding

From --------------;