Obiee - physical layer

Question

Hi,
I'm new to obiee tool.
my dimension table have composite primary keys (3 keys - suppose employee id, employee ssn, phone no)
and my fact table have (2 keys - employee id, employee ssn )
then, how do we do physical join in physical layer ?
Do, we need to create 2 alias tables and join to my fact table ?
or, else can i use expression builder in the physical diagram..physical join ?

Answer 1

Hi,
This is why you go for alias tables ..
To set up multiple tables, each with different keys, names, or joins, when a single data source table needs to serve in different semantic roles. Setting up alias tables in this case is a way to avoid triangular or circular joins.
For example, an order date and a shipping date in a fact table may both point to the same column in the time dimension data source table, but you should alias the dimension table so that each role is presented as a separately labeled alias table with a single join. These separate roles carry over into the business model, so that "Order Date" and "Ship Date" are part of two different logical dimensions. If a single logical query contains both columns, the physical query uses aliases in the SQL statement so that it can include both of them.
You can also use aliases to enable a data source table to play the role of both a fact table, and a dimension table that joins to another fact table (often called a "fan trap").
To include best practice naming conventions for physical table names. For example, you can prefix the alias table name with the table type (such as fact, dimension, or bridge), and leave the original physical table names as-is. Some organizations alias all physical tables to enforce best practice naming conventions. In this case, all mappings and joins are based on the alias tables rather than the original tables.
Now for creating joins you can make use of expression builder to have Primary Key and Foreign Key Relationships OR you can also have Complex Joins here over nonforeign key and primary key columns. When you create a complex join in the Physical layer, you specify the expression for the join. Like
Employee.employeeID=Fact.EmployeeId
and Dim table.deptname <> 'ABC'
You, can also have case statements here...
Hope this clears your funda regarding Alias Tables & Joins. Expression Builder is just the utility for developers to select the table, columns, expressions, variables and may other functions available.