Join tables

A join table is a temporary logical table that has the following properties and functions:

  • Resides only in memory
  • Contains no records
  • Is not written to the database
  • Points to the data in the device table and related attribute table.
  • Does have a dbdict

The join table temporarily joins the fields in the device table record with the fields in the attribute table. Join tables are never populated. They only serve as pointers to fields that are extracted from the device table and the attribute tables and they display the joined data in a form. When you make changes to the join table by making changes to the data in a form, Service Manager writes the changes to the original device and attribute tables.

As a rule, the join table name hasdevice as a prefix and the attribute table name as the suffix. For example, the join table name for a PC component is devicepc. The form that displays the joined data is named device.attribute, for example, device.pc.

Join tables are named according to the following conventions:

  • Join table name is a combination of the device table name and its attribute table name (device.attribute.name).
  • Logical.name field is the unique identifier in the dbdict for the device and attribute tables.