On PointBase, when I am trying to delete a PK Column which has referential
integrity constraints,
"THE ERRORS SHOULD BE SHOWN AS ERROR MESSAGES", but it is being shown as
Exceptions.

In the Bundled PointBase Sample database, trying to delete 
SALES_REP_TBL.SALES_REP_NUM
throws java.io.IOException :
Fri Jan 11 12:03:43 PST 2002: java.io.IOException: Unable to execute a command:
alter table "PUBLIC"."SALES_REP_TBL" drop "SALES_REP_NUM"
Referential Integrity Violation. PUBLIC.ORDER_TBL references
PUBLIC.SALES_REP_TBL
java.io.IOException: Unable to execute a command:
alter table "PUBLIC"."SALES_REP_TBL" drop "SALES_REP_NUM"
Referential Integrity Violation. PUBLIC.ORDER_TBL references
PUBLIC.SALES_REP_TBL
        at
org.netbeans.modules.db.explorer.infos.ColumnNodeInfo.delete(ColumnNodeInfo.java:71)
        at
org.netbeans.modules.db.explorer.nodes.DatabaseNode.destroy(DatabaseNode.java:157)
        at
org.openide.explorer.ExplorerActions$DeleteActionPerformer$DestroyAtomic.invoke(ExplorerActions.java:527)
        at $Proxy3.run(Unknown Source)
        at
org.openide.filesystems.EventControl.runAtomicAction(EventControl.java:89)
        at
org.openide.filesystems.FileSystem.runAtomicAction(FileSystem.java:388)
        at
org.openide.explorer.ExplorerActions$DestroyInvoker.run(ExplorerActions.java:568)
        at
org.openide.explorer.ExplorerActions$DeleteActionPerformer.doDestroy(ExplorerActions.java:494)
        at
org.openide.explorer.ExplorerActions$DeleteActionPerformer.performAction(ExplorerActions.java:463)
        at
org.openide.util.actions.CallbackSystemAction.performAction(CallbackSystemAction.java:109)
        at
org.openide.util.actions.CallableSystemAction.actionPerformed(CallableSystemAction.java:69)
        at org.netbeans.core.ModuleActions$1.run(ModuleActions.java:105)
        at org.openide.util.Task.run(Task.java:152)
[catch] at
org.openide.util.RequestProcessor$ProcessorThread.run(RequestProcessor.java:622)