Managing Joins

When you add more than one table to the Backend Data Tank for a resource, Percussion automatically generates any joins it can guess. In most cases, any columns that share the same name will be joined. All joins created by Percussion are inner joins by default.

Data on the left-hand-side of the join can be translated before comparison. The first table selected when you create a join is always the left-hand-side of the join, and is indicated by an arrow. (Note: in joins generated by Percussion, any tables that already exist in the Backend Data Tank will be the left-hand-side of the join.)

To maintain joins, use the Join editor. To access the Join editor, double-click on the Backend Data Tank.

To add a new join select the table column in the first table, drag your cursor to the column in the second tab and release. Percussion creates the join between the two tables. The join is represented by a line between the columns in the two table objects.

To change the properties of a join:

1. Right-click on the join whose properties you want to manage.

   The Workbench displays the Join Properties dialog.

2. To change the Join Type, select the radio button for the type you want. Options are:
   • Inner Join (default)
   • Left Outer Join
   • Right Outer Join
   • Full Outer Join
3. To translate data on the left-hand-side of the join, check the Enable join translation to be applied to the left side checkbox. Click the [Edit Formula] button to display a function editor you can use to select the function to perform the conversion and to define the values for any parameters in the function.
4. Click the [OK] button to save your changes.