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View a table hierarchy and the extension model

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View a table hierarchy and the extension model

The extension model used by a table is not immediately apparent. While a hierarchy can use a single physical table, the platform displays tables as if each logical table has a unique physical table. For example, when specifying a table for a workflow, you can select Change [change_request] or Incident [incident] even though the parent table, Task [task], uses a single physical table.

Before you begin

Role required: admin

About this task

Administrators can view the status of flattened table hierarchies, but cannot flatten additional hierarchies. You can configure the form to add the Extension model field if necessary.


  1. Navigate to System Definition > Tables.
  2. Select a table record.
  3. Review the Extension model field value, which indicates whether the table hierarchy uses multiple unique tables or a single flat table.
    • None: Indicates that the table uses the table per class model. Defines a unique physical table per logical table in a hierarchy. For example, there are separate physical tables for Task [task], Incident [incident], Problem [problem], and Change [change_request] on the MySQL database.
    • Table per hierarchy: Defines a single physical table per logical table hierarchy. For example, there is a single Task [task] table on the MySQL database that contains all the Task, Incident, Problem and Change records. This single physical table is represented as separate logical tables.