Joined Columns

•In USoft Definer, a joined column is a virtual column take a value from a direct parent table. In USoft 9.1, virtual columns are deprecated.

•In USoft Windows Designer, a joined column is an additional, displayed or hidden, field that you will have added to an info box in a window class you are painting. Such a joined column takes its value by copying a stored column value from a related parent table or a higher-level ancestor table. The info box that contains the joined column is based on a child table.

Joined columns are useful if you are painting an end user screen based on a child table and you want to show information from higher-level ancestor tables that is meaningful to the end user.

In a Travel Agency, you are creating a GUI based on a Travellers table. Each Traveller is related to a Reservation by a number ID. That Reservation is related by another number ID to the tour product that the Reservation is for. Each tour product, in turn, is related to a Tour Programme. The end user of the GUI needs information from the Tour Programme to make sense of where the displayed Travellers are travelling to.

To add Joined Columns:

1.	Use the Windows Designer catalog to open the appropriate window class. This will be a class based on a child table.

2.	In the design view, select the Info Box into which you want to insert the joined column(s).

3.	From the menu bar, choose Insert, Joined Columns... This option is available only if your info box is for a child table.

The Insert Joined Columns dialog appears. On the left, this dialog represents the relationships that the child table is in. If there are grandparents or other ancestors, you can expand the tree view until you reach the highest-level parent:

4.	In the left-hand pane, select the relationship level from where you want to take values for your Joined Column(s).

5.	In the right-hand pane, select the column or columns that you want to add to your info box as Joined Column(s). Press OK. Save work.

The result is visible in the design tree (on the right of your screen) as an Extra Query object with a name such as "VIRTUAL_TYPE 1". To view the functionality, open the object in the Property Inspector. Inspect the values that USoft has generated for the Joined Columns, Relationships and Underlying Query properties.

Using the Yes Action and No Action properties, you can define additional action that must be taken if a value for the Joined Column is, or is not found. For this technique, see the examples in the Extra Queries help topic.