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Oracle Substitutable Types

Oracle Tips by Burleson Consulting

Steve Karam, a respected OCM holder has a great study on using Oracle Substitutable Types in table definitions when you need to store different information about the same "type" of thing.  For example, a VEHICLE table might need to store unique information about boats (tonnage, sail size), and aircraft (last FAA inspection), same object, but with very different data.

Oracle Oracle Substitutable Types allow for polymorphism (object-orientation) because you can declare various types of an entity and store very different data within the same table rows.

Karam has an outstanding example of Oracle substitutable types:

"Let?s say you had to create a table that could support every different kind of electronic computing device. . .

You can make a single table with hundreds of columns, most of them nullable, that can handle all of it. Or you can make a table with tons of columns like STRING1, STRING2, NUMBER1, NUMBER2 to handle any eventuality. Or, you can just make a different table for every single device out there. Lastly, you can make other tables that have two vague columns, NAME and VALUE, so you can have as many rows as you want to describe the object in any way you like?but what happens when you have to do an AND or OR where clause against it? You?re stuck with UNIONs and such and performance goes downhill. . .

Enter object oriented Oracle, using substitutable types. How would you like a single column that can hold all of these columns and more that?s extremely scalable and easy to manage? Yes please. . .

What we will do is create a base table to hold all these items with columns that pertain to the overall concept."


If you like Oracle tuning, you may enjoy my new book "Oracle Tuning: The Definitive Reference", over 900 pages of BC's favorite tuning tips & scripts. 

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.



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