In my opinion; common re-usable code that manipulates the data and need performance at the database level needs to reside in the database in the form of stored procedure and triggers where the queries can be tweaked. If it is business logic then it should be in the middle tier. Data that needs to be modified and inputs validated resides at the client level avoiding unnecessary network round-trips. There are several other factors the DBA and architect have to take into account like latency, network round trip etc. All this should come with experience. Both Database and application group should work in tandem; The reason one will not agree with other are for reasons listed below: 1. politics 2. job security 3. bragging rights 4. blame game thanks.

in OOP use duck typing as means to avoid using if's and case statement to invoke objects of different classes. [^]