If you have instance data that is common across more than one class you can use this form to build the queries to display this data.
For example if you have a class for flow transmitters and one for other transmitters this will allow you to build a (read only) query containing the data each has in common, eg Scale and Range.
Note - these are read only Union queries
To invoke this form select multiclass instances from the Query designer.
The shared fields - those that are used in more than one class are listed on the left
As you select shared fields, the classes that contain your selections are then listed in the middle.
You can choose which classes to include in the middle and include the fields on the right
"Multi Class Instances" in the Query Design form calls up the Shared Instance Query Builder.
Add ClassName puts the name of the class as the first column.