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Oracle PL/SQL Programming: A Developer's Workbook
book

Oracle PL/SQL Programming: A Developer's Workbook

by Steven Feuerstein, Andrew Odewahn
May 2000
Intermediate to advanced content levelIntermediate to advanced
594 pages
11h 32m
English
O'Reilly Media, Inc.
Content preview from Oracle PL/SQL Programming: A Developer's Workbook

Intermediate

Q:

16-22.

Executing the procedure results in an error because DBMS_SQL treats :OLD and :NEW as ordinary bind variables; consequently, it complains that not all the binds have been assigned. In short, the :OLD and :NEW predicates can’t be directly referenced in statements executed via dynamic SQL.

Q:

16-23.

The following template shows how to raise an error when a DML statement violates a business rule:


/* Filename on web page: secure_del_trigger.sql */
CREATE OR REPLACE TRIGGER secure_del_trigger
   BEFORE DELETE
   ON emp
   FOR EACH ROW
DECLARE
   unauthorized_deletion EXCEPTION;
BEGIN
   IF <your business rule is violated> THEN
     RAISE unauthorized_deletion;
   END IF;
EXCEPTION
   WHEN unauthorized_deletion
   THEN
      raise_application_error (-20500,
        'This record cannot be deleted');
END;
/

Q:

16-24.

(b). Object privileges must be granted directly to the trigger owner and cannot be acquired through database roles.

Q:

16-25.

The triggers are:

  1. Invalid. The trigger explicitly calls SQL COMMIT, which is forbidden in Oracle.

  2. Invalid. The trigger dynamically creates a sequence via the DDL statement CREATE SEQUENCE that is issuing an implicit commit. SQL DDL statements are not allowed in triggers because DDL statements issue implicit COMMITs upon completion.

  3. Valid. A system trigger is the only type of trigger that allows CREATE/ALTER/DROP TABLE statements and ALTER…COMPILE in the trigger body, despite the fact that ...

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Publisher Resources

ISBN: 9781449324070Supplemental ContentErrata Page