PL/SQL Fehlerbehandlung

Ja, es ist richtig: meine Einträge hier werden in letzter Zeit kürzer und kürzer. Daran werde ich aber auch heute nichts ändern, denn eigentlich will ich gerade nur einen Link unterbringen: Steven Feuerstein listet in seinem Artikel Nine Good-to-Knows about PL/SQL Error Management- nun ja: neun interessante Punkte auf, die man beim Exception Handling in PL/SQL berücksichtigen sollte. Zu den wichtigsten Hinweisen gehören aus meiner Sicht:
  • "An exception raised does not automatically roll back (more...)

Bind Variables

This example, tested on Oracle 11, shows how you can define bind variables in SQL*Plus, assign values to them in PL/SQL then display those values afterwards back in SQL*Plus:

SQL> variable bv1 varchar2(3)
SQL> variable bv2 number
SQL> begin
  2  select 'ABC' into :bv1 from dual;
  3  select 123 into :bv2 from dual;
  4  end;
  5  /

PL/SQL procedure successfully completed.

SQL> print bv1


SQL> print bv2


#DB12c feature – Secure External Procedures with DBMS_CREDENTIAL

Oracle Database 12c enables enhanced security for extproc by authenticating it against a user-supplied credential. This new feature allows the creation of a user credential and links it with a PL/SQL library object. Whenever an application calls an external procedure, the extproc process authenticates the connection before loading the shared library. The DBMS_CREDENTIAL package is … Continue reading

Temporal validity, multiple end dates

Recently I got involved in a question on Temporal Validity Periods together with Chris Saxon, one of the askTom-answer team.

The question was along the lines of: "What if I have a single start date but two possible end dates. One of the end dates is filled automatically by a background proces (could be a job) while the other one is to signal that the end date is set manually by the user. Could you (more...)

Designing PL/SQL Programs: Series home page

Designing PL/SQL Programs is a succession of articles published the articles in a nonlinear fashion. Eventually it will evolve into a coherent series. In the meantime this page serves as a map and navigation aid. I will add articles to it as and when I publish them.


Designing PL/SQL Programs

Principles and Patterns

Introducing the SOLID principles
Introducing the RCCASS principles
The Dependency Inversion Principle: a practical example

Software Architecture

Interface design

Tools and Techniques

The Dependency Inversion Principle: a practical example

These design principles may seem rather academic, so let's look at a real life demonstration of how applying Dependency Inversion Principle lead to an improved software design.

Here is a simplified version of an ETL framework which uses SQL Types in a similar fashion to the approach described in my blog post here. The loading process is defined using an abstract non-instantiable Type like this:

create or replace type load_t force as object
( txn_date (more...)

Introducing the RCCASS design principles

Rob C Martin actually defined eleven principles for OOP. The first five, the SOLID principles, relate to individual classes. The other six, the RCCASS principles, deal with the design of packages (in the C++ or Java sense, i.e. libraries). They are far less known than the first five. There are two reasons for this:

  • Unlike "SOLID", "RCCASS" is awkward to say and doesn't form a neat mnemonic. 
  • Programmers are far less interested in (more...)

Introducing the SOLID design principles

PL/SQL programming standards tend to focus on layout (case of keywords, indentation, etc), naming conventions, and implementation details (such as use of cursors).  These are all important things, but they don't address questions of design. How easy is it to use the written code?  How easy is it to test? How easy will it be to maintain? Is it robust? Is it secure?

Simply put, there are no agreed design principles for PL/SQL. So it's (more...)

Also Extensions Created Because of SQL Plan Directives Can Invalidate Packages – Take Two

In a previous post I described a situation where the creation of an extension, independently of whether it’s carried out manually by a person or automatically by the database engine, can lead to the invalidation of PL/SQL objects. In this second post on that subject, I describe, with the help of an example (I love examples!) based on the extension_invalidate_pkg_remote.sql script, what can happen when the table on which the extension is created (more...)

Default parameter values in package subprograms

For a procedure (or function) in a package, you can assign default values only in the package specifications without assigning them in the package body:

PROCEDURE set_global (p_num IN NUMBER DEFAULT 1);

Package TEST_DEFAULT_PKG compiled

No errors.
PROCEDURE set_global (p_num IN NUMBER) AS

Package body TEST_DEFAULT_PKG compiled


PL/SQL context switch

Whenever you use PL/SQL in SQL statements, the Oracle engine needs to switch from doing SQL to doing PL/SQL, and switch back after it is done. Generally, this is called a “context switch”. This is an example of that:

-- A function that uses PL/SQL 
create or replace function add_one( value number ) return number is
        l_value number(10):= value;
        return l_value+1;
-- A SQL statement that uses the PL/SQL function
select sum(add_one(id))  (more...)

Logical operators in RETURN clause of a function

Here is what I learnt today.

You can use logical operators in the RETURN clause of a function whose return type is BOOLEAN. So for example, you can write a function with the following structure:

create or replace function test_fn(p_param varchar2)
return boolean
l_value varchar2(10):= 'TEST';
return false
or p_param = l_value
or length(p_param) = 5 ;
show errors;

The logical truth table is used to evaluate the expression in the RETURN clause (more...)

My Oracle Database Developer Choice Awards 2015

Earlier this week, Santa's little helper (ie DHL) knocked on my door and delivered a package containing my trophies from the Oracle Database Developer Choice Awards 2015. I was nominated in three categories, and won awards in two of them: Application Express and ORDS.

Here's a video from the award ceremony at Oracle OpenWorld 2015:

I'd like to send a big THANK YOU to everyone who voted for me, and also to Oracle for (more...)

Updating Identity Columns

During my presentation "Oracle 12c for Developers" at the Sloveninan and Croatian User Groups I got the same question twice about Indentity Columns:

Is it possible to update an Identity Column?
During the presentation I show how it is not possible to insert a value for a "Generated Always Identity" column.
Let's take a look at an example:

SQL> create table t
2 (id number generated as identity
3 ,name varchar2(35)
4 );

Table created.


Oracle package for HTTPS/HTTP[version 0.2]

A couple days ago i created simple package for HTTPS/HTTP, but I’ve decided now to improve it:

  1. Timeout parameter – it would be better to control connection time;
  2. Simple page parsing with PCRE regular expressions – to speed up and simplify page parsing, because if you want to get big number matched expressions from CLOB with regexp_xxx oracle functions, you have to call these functions many times with different [occurance] parameters, passing/accessing to the (more...)

Very simple oracle package for HTTPS and HTTP

I don’t like to import certificates, so i cannot use httpuritype for HTTPS pages and I decided to create package which will work with https as http.
It was pretty easy with java stored procedures :)

java source: xt_http.jsp
create or replace and compile java source named xt_http as
package org.orasql.xt_http;


Sending SMS text messages from PL/SQL

Do you need to send SMS (Short Message Service) text messages from your Oracle database using PL/SQL? This is actually quite easy to do, the only hard part is deciding on which SMS gateway to use. You need to sign up with a gateway provider to get a username and password to use the gateway, and you typically pay some cents for each message you send.

Do a google search for "sms gateway api (more...)

My nominations for the Oracle Database Developer Choice Awards 2015

I'm honored to have been nominated for the Oracle Database Developer Choice Awards 2015, in no less than three (!) categories: PL/SQL, Application Express (Apex) and Oracle REST Data Services (ORDS).

Here's a short video that explains what the Oracle Database Developer Choice Awards are all about:

If you are a regular reader of my blog, you are probably familiar with my contributions to the Oracle Database Developer community, but here is (more...)

Autonomous transaction to the rescue

Rounding Amounts, the missing cent: with the MODEL clause

Rounding amounts may lead to rounding-issues, I have written how this may be resolved in a previous blogpost using some analytic functions.
Playing around a little bit, I also came up with a method to resolve the rounding difference with the MODEL clause.

To create an example, first let's create a table with only three records in it.

SQL> create table t
2 as
3 select rownum + 42 id
4 from dual
5 connect (more...)