Think of this scenario

Invoice 1:n Invoiceline

Inserting something in InvoiceLine. Invoiceline needs a parent pointer, if not, we get an insert error

Now suppose we have a cascade update, ie Id update on Invoice cascade updates InvoiceLine

The update on InvoiceLine needs not check the parent pointer if it is a cascaded update from Invoice


That is wat the code does

If ( no cascadeparent or (cascasdeparent <> Contacts) )
    If ( indexexpr changed )
       check relation
    endif
endif

>Bellow is the code I generated for a test database. You're right, that it has to be more robust. E.g. if triggerlevel <>1 I need to check, if it is the same parent initiated it.
>But in this code I do not understand, why it is telling about Insert trigger violated while it is an Update trigger?
>

>********************************************************************************
>procedure __RI_UPDATE_calls
>** "Referential integrity update trigger for" calls
>LOCAL llRetVal
>llRetVal = .t.
>PRIVATE pcParentDBF,pnParentRec,pcChildDBF,pnChildRec,pcParentID,pcChildID
>PRIVATE pcParentExpr,pcChildExpr
>STORE "" TO pcParentDBF,pcChildDBF,pcParentID,pcChildID,pcParentExpr,pcChildExpr
>STORE 0 TO pnParentRec,pnChildRec
>IF _triggerlevel=1
>  BEGIN TRANSACTION
>  PRIVATE pcRIcursors,pcRIwkareas,pcRIolderror,pnerror,;
>  pcOldDele,pcOldExact,pcOldTalk,pcOldCompat,PcOldDBC
>  pcOldTalk=SET("TALK")
>  SET TALK OFF
>  pcOldDele=SET("DELETED")
>  pcOldExact=SET("EXACT")
>  pcOldCompat=SET("COMPATIBLE")
>  SET COMPATIBLE OFF
>  SET DELETED ON
>  SET EXACT OFF
>  pcRIcursors=""
>  pcRIwkareas=""
>  pcRIolderror=ON("error")
>  pnerror=0
>  ON ERROR pnerror=rierror(ERROR(),message(),message(1),program())
>  IF TYPE('gaErrors(1)')<>"U"
>    release gaErrors
>  ENDIF
>  PUBLIC gaErrors(1,12)
>  pcOldDBC=DBC()
>  SET DATA TO ("CONTACTS")
>ENDIF first trigger
>LOCAL lcParentID && parent's value to be sought in child
>LOCAL lcOldParentID && previous parent id value
>LOCAL lcChildWkArea && child work area handle returned by riopen
>LOCAL lcChildID && child's value to be sought in parent
>LOCAL lcOldChildID && old child id value
>LOCAL lcParentWkArea && parentwork area handle returned by riopen
>LOCAL lcStartArea
>lcStartArea=select()
>llRetVal=.t.
>lcChildWkArea=select()
>IF _triggerlevel=1 or type("pccascadeparent")#"C" or (NOT pccascadeparent=="CONTACTS")
>  SELECT (lcChildWkArea)
>  lcChildID=CONTACT_ID
>  lcOldChildID=oldval("CONTACT_ID")
>  pcChildDBF=dbf(lcChildWkArea)
>  pnChildRec=recno(lcChildWkArea)
>  pcChildID=lcOldChildID
>  pcChildExpr="CONTACT_ID"
>  IF lcChildID<>lcOldChildID
>    lcParentWkArea=riopen("contacts","contact_id")
>    IF lcParentWkArea<=0
>      IF _triggerlevel=1
>        DO riend WITH .F.
>      ENDIF at the end of the highest trigger level
>      SELECT (lcStartArea)
>      RETURN .F.
>    ENDIF not able to open the child work area
>    pcParentDBF=dbf(lcParentWkArea)
>    llRetVal=SEEK(lcChildID,lcParentWkArea)
>    pnParentRec=recno(lcParentWkArea)
>    =rireuse("contacts",lcParentWkArea)
>    IF NOT llRetVal
>      pnError = rierror(-1,"Insert restrict rule violated.","","")
>      IF _triggerlevel=1
>        DO riend WITH llRetVal
>      ENDIF at the end of the highest trigger level
>      SELECT (lcStartArea)
>      RETURN llRetVal
>    ENDIF no parent
>  ENDIF this value was changed
>ENDIF not part of a cascade from "contacts"
>lcParentWkArea=lcChildWkArea
>IF _triggerlevel=1
>  do riend with llRetVal
>ENDIF at the end of the highest trigger level
>SELECT (lcStartArea)
>RETURN llRetVal
>** "End of Referential integrity Update trigger for" calls
>

>
[snip]