Examine Logical Joins, Logical Table Sources, Logical Columns in OBIEE

12 October, 2020


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Examine Logical Joins:

  1. Right-click the Sample Sales business model and select Business Model Diagram -->  Whole Diagram to open the Business Model Diagram.
  2. If necessary, rearrange the objects so that the join relationships are visible.


Because you dragged all tables simultaneously from the Physical layer onto the business model, the logical keys and joins are created automatically in the business model. This is because the keys and join relationships were already created in the Physical layer. However, you typically do not drag all physical tables simultaneously, except in very simple models. Later in this tutorial, you learn how to manually build logical keys and joins in the Business Model and Mapping layer. The process is very similar to building joins in the Physical layer.

3. Double-click any one of the joins in the diagram to open the Logical Join dialog box. In this example, the join between D1 Time and F1 Revenue is selected.

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Notice that there is no join expression. Joins in the BMM layer are logical joins. Logical joins express the cardinality relationships between logical tables and are a requirement for a valid business model. Specifying the logical table joins is required so that Oracle BI Server has the necessary metadata to translate logical requests against the business model into SQL queries against the physical data sources. Logical joins help Oracle BI Server understand the relationships between the various pieces of the business model. When a query is sent to Oracle BI Server, the server determines how to construct physical queries by examining how the logical model is structured. Examining logical joins is an integral part of this process. The Administration Tool considers a table to be a logical fact table if it is at the “many” end of all logical joins that connect it to other logical tables.

4 . Click OK to close the Logical Join dialog box.

5. Click the X to close the Business Model Diagram.

Examine Logical Columns:

1 . Expand the D1 Time logical table.

Notice that logical columns were created automatically for each table when you dragged the alias tables from the Physical layer to the BMM layer.


Examine Logical Table Sources

1 . Expand the Sources folder for the D1 Time logical table. Notice there is a logical table source, D1 Time. This logical table source maps to the D1 Time alias table in the Physical layer.


2 . Double-click the D1 Time logical table source (not the logical table) to open the Logical Table Source dialog box.


3 . On the General tab, rename the D1 Time logical table source to LTS1 Time. Notice that the logical table to physical table mapping is defined in the "Map to these tables" section.


4 . On the Column Mapping tab, notice that the logical column to physical column mappings is defined. If mappings are not visible, select Show mapped columns.


5 . You learn more about the Content and Parent-Child Settings tabs later in this tutorial when you build logical dimension hierarchies. Click OK to close the Logical Table Source dialog box. If desired, explore logical table sources for the remaining logical tables.


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