Obsessed with Oracle PL/SQL

A few weeks ago, Mike Hichwa asked me to come up with a package that would implement a simple alerting utility: specify a triggering event (based on a query or a PL/SQL expression) and then take the specified actions when it is triggered. Seeing as he is my boss, I said "OK" and got to work (my favorite kind of work: writing some PL/SQL code). We did our usual bit to expand scope, then did our usual bit to agree that this is enough for a first pass. And then Mike said: "Go ahead and write a blog post about it, share it with the community." So here goes. The basic idea is we start up a job using DBMS_SCHEDULER that runs every N minutes. When it runs, it checks to see if any alerts need to be triggered. If so, it then takes one or more actions associated with that alert. Let's start with our tables. Utility configuration How often should the job wake up? Should it disable checking for alerts? What is the name of the "callout" for sending ema...

There are special member methods -  map  or  order  methods - that we use to tell Oracle Database how to compare two objects of the same datatype. This capability is critical when we want to perform an equality test in PL/SQL or when sorting objects in SQL. There is no default way to do this. In other words, if I create a simple object type, add it as a column to a table, and try to compare or sort, all I get are errors. Let's take a look. First I will create a table that has an object type as a column and add a couple of rows. CREATE TYPE food_ot AS OBJECT ( name VARCHAR2 (100), food_group VARCHAR2 (50), grown_in VARCHAR2 (100) ) NOT FINAL / CREATE TABLE meals ( served_on DATE, main_course food_ot ); / BEGIN INSERT INTO meals (served_on, main_course) VALUES (SYSDATE, food_ot ('Shrimp cocktail', 'PROTEIN', 'Ocean')); INSERT INTO meals (served_on, main_course) VALUES (SYSDATE + 1, food_ot ('House Salad...

So far in my series on object-oriented development in Oracle Database, all manipulation of object type instances have taken place in PL/SQL. But as you may have guessed from the fact that you "CREATE OR REPLACE" object types, those types are also available for us in SQL. You can create relational tables of object types, called object tables. You can also define columns of relational tables whose datatypes are object types. In this post, I will explore both of these approaches. All the code you see below may be found in this  LiveSQL script , so you can get to know these features by playing around with them yourself. Object Tables It's easy to create object tables and work with the instances in those tables (both selecting and changing rows of data). Here's a simple example: CREATE TYPE food_ot AS OBJECT ( name VARCHAR2 (100), food_group VARCHAR2 (50), grown_in VARCHAR2 (100) ) NOT FINAL / CREATE TABLE food_table OF food_ot (CONSTRAINT food_ta...

On September 16, Larry Ellison announced a new Always Free tier for Oracle Cloud, which (for me) most importantly includes an Always Free Autonomous Oracle Database. For nothing but the "cost" of providing your credit card information (which is only used for identification purposes and is henceforth ignored until you decide to upgrade to a paid service), everyone in the world now can use the most powerful, most advanced database in the world FOR FREE. Of course, there are limits. But oh my what generous limits they are! Get lots more details here . And it's not just the amazing Autonomous Database (in both transaction processing and data warehouse flavors). You get Oracle Application Express (APEX) so you can build websites  writing very little code, and taking full advantage of your SQL and PL/SQL skills. You get SQL Developer to write what code you need and manage your database. You get Oracle Rest Data Services to build REST endpoints against your...

Find below the list of my blog posts in a series on working with object types (a.k.a, classes) in Oracle Database and, specifically, PL/SQL. This series is not intended to offer an in-depth training on object-oriented development; instead, it introduces basic O-O concepts and shows how they are implemented in Oracle Database with PL/SQL. Introduction to Object Types, Part 1 Object Types and Inheritance, Part 2 Object Types Methods, Part 3 Using Object Types in Relational Tables, Part 4 Comparison Methods for Object Types, Part 5 Dynamic Polymorphism - Why, What, How, Part 6 Each post also contains a link to a LiveSQL script, so you can try out all the code yourself.

Packages have subprograms (procedures and functions). Object types have methods. Object type methods are, still, procedures and functions. But there are also different types and characteristics of methods that only make sense in an object type, which supports inheritance and dynamic polymorphism. In this post, 3rd in my series on object types, I explore Static methods  Member methods  Non-instantiable methods  Invoking methods of super types All the code you see below can be run in Oracle LiveSQL through this script . Member Methods Member methods are methods applied to an instance of the type. Almost all the methods you ever write for an object type will be a member method. Assuming you are already familiar with writing PL/SQL functions and procedures, the most important thing to come up to speed on is the SELF value. Member methods have a built-in (implicit) parameter named SELF that denotes the object instance currently invoking the method. We'll...

When more than one subprogram (procedure or function) in the same scope share the same name, the subprograms are said to be overloaded. PL/SQL supports the overloading of procedures and functions in the declaration section of a block (named or anonymous), package specifications and bodies, and object type definitions. Overloading is a very powerful feature, and you should exploit it fully to improve the usability of your software. Before exploring some of the details of overloading, a short quiz: Which of the following is another name for overloading? Dynamic Polymorphism Interface Inheritance Static Polymorphism Multiple Monomorphism In a poll I conducted on Twitter , we saw the following results: And I was very glad to see this, because Static Polymorphism is, indeed, another name for overloading, and here's why: With overloading, at the time your code is compiled, PL/SQL resolves all references to named elements, such as a function invocation. If there is more ...