Logical Tables
· Logical tables exist in the BMM layer and represent fact or dimension data.
· Logical fact tables have a yellow icon and logical dimension tables have a white icon.
Logical Table: Properties
· Bridge table is checked to resolve many to many relations between the tables.
· Sources tab contains the LTS, keys tab contains primary key and foreign keys tab contain foreign keys.
· You can re-order the columns in the table.
· The logical schema defined in each business model needs to contain at least two logical tables and you need to define relationships between them.
· You can create the logical tables either by dragging the physical table or manually creating it on the BMM layer.
· When you drag physical tables (with key and foreign key relationships defined) to a business model, logical keys and joins are created that mirror the keys and joins in the physical layer.
Logical Table Sources (LTS)
· Logical table sources define the mappings from a logical table to a physical table. A logical table’s Sources folder contains the logical table sources.
· Logical table source can have more than one sources from the physical layer. For example, revenue information may come from multiple data sources in a business. So, you can add these three sources to one LTS with joins. Another example could be to combine detailed level data and aggregated data, the OBI server will fetch the best source when queried on the reports.
· When you create logical tables and columns by dragging from the Physical layer, the logical table sources are generated automatically.
Logical Table Source (LTS): Properties
· Double click on the LTS to open the LTS properties screen.
· The general tab contains name other sources with join relations.
· Use the Column Mapping tab of the Logical Table Source dialog box to build, view, or modify logical to physical column mappings.
· A mapping can also be used to specify transformations that occur between the Physical layer and the Business Model and Mapping layer (Example: changing an integer data type to a character type or find a percentage of sales per unit of population.
· The Content tab is used to describe the aggregation levels (logical level or by column), to mention the fragmentation content, filter data by using where clause section and also to select distinct values.
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