Because of the data warehouse design, data may be stored in the physical tables in the normalized way. That means some columns are stored in different tables. This kind of design is called as the snowflake schema. For example, let's assume that the product data is spread into different physical tables, for example, the price information doesn't exist in the product table and it's stored in the price list table. Another example is that supplier data can be stored in another table such as the suppliers table.
When this is the case, there's a business solution in Oracle Business Intelligence. We can add multiple sources to existing logical table sources.