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I am trying to see how input validation addresses cases where the constraint is based on what else is in the database. It is conceptually much simpler and less

I am trying to see how input validation addresses cases where the constraint is based on what else is in the database. It is conceptually much simpler and less error prone to let that class of issues be enforced only by the database rather than asking the db first "is this ok" and if so then doing another round trip to insert it (to be safe you'd have to lock the table). Now, PostgreSQL can do any data validation you want to do in the application, it can do so at least partially declaratively. You can then pass back messages that the application can use in error handling. I am actually working on frameworks which essentially delegate most of this to PostgreSQL. It's a very powerful approach but it means the db just doesn't trust the application.

masklinn 13y ago
> It's a very powerful approach but it means the db just doesn't trust the application. Which has its advantages. The DB essentially becomes an API/service used by the application rather than an integral part thereof, and thus multiple applications can be cleanly plugged into the database instead of an "owner" application providing a service backed by the owned DB.
- einhverfr 13y ago
  > The DB essentially becomes an API/service used by the application.... Exactly, which is what Martin Fowler is pushing with NoSQL... The idea that many people have been using RDBMS's as encapsulated databases for decades is usually lost on the NoSQL marketing though.