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Oracle Database Constraints : Formal PredicatesThis section of the website talks about Oracle database constraints.
To my knowledge, Oracle is the database vendor that has the best support for declarative constraints.
What do I mean by declarative? That constraints are defined in DDL (Data Definition Language): This means that you do not have to code them in your application.
Oops: Let's talk a little about that: Where should constraints be defined: In the database, or in your application?
In my view, there is no discussion about where to handle database constraints: In the database, not in the application. Why?
Applications come and go, but your database will be used by several applications. If you include constraints in your application, you will have to copy that code into new applications as well.
You're easily able to see the consequences: Code must be maintained in several places, it will (most likely) perform poorer than if in the database, and most importantly: What if you forget to include a constraint in your new application?
But, Oracle database constraints, while giving you some possibilities for declarative constraints, still is not good enough.
This series of articles explain the possibilities, but also the restrictions you will meet when using Oracle database constraints.
After you have gone through the articles, at the bottom of this page, we will look into a few possible solutions for including constraints in other ways than the (limited) possibilities that Oracle is giving you.
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