Trigger Cross-references

Trigger Cross-references Introduction

A trigger causes something else to happen. In VA FileMan, you can set up a trigger so that the entry of data in one field automatically updates a second field value. Since a trigger is considered a type of cross-reference on the field for which data is entered, a trigger is logically created under the Cross-Reference a Field or File option in the Utility Functions menu.

To understand how a trigger is set up, you must first understand that every cross-reference specification describes both:

• what happens when a new value is entered, either initially or when an existing value is changed (set logic)
  
  
• what happens when an old value is changed or deleted (kill logic)

In other words, when patient SMITH,JACK is first entered into a file of patients, a SMITH,JACK regular cross-reference on the name is built (and nothing is deleted). Then, when this name is edited (changed) to be SMITH,JOHN Q--two things happen:

• the SMITH,JACK regular cross-reference is deleted
  
  
• a SMITH,JOHN Q regular cross-reference is created

Finally, when this patient is deleted from the file, the SMITH,JOHN Q cross-reference is deleted (and none is created).

When you are using the Cross-Reference a Field or File option and you specify a trigger, you must identify both what happens when a new field value is entered (either initially or through an edit on an existing value) and when an old value is changed or deleted.

You must be careful in setting up any trigger cross-reference since unexpected effects can sometimes result. Note that at the moment when the trigger actually occurs:

• No validity check is made on the value being forced into the field (in other words, the value doesn't go through the triggered field's INPUT transform).
  
  
• Cross-references (if any) do occur on the triggered field (e.g., a triggered field can in turn trigger other fields in a chain reaction!).

Reviewed/Updated: March 4, 2007