Depends on your abstraction system. If we're talking about SQL, the incompatibilities abound. And ORM's or other libraries tend to be either very, very complex

Depends on your abstraction system. If we're talking about SQL, the incompatibilities abound. And ORM's or other libraries tend to be either very, very complex or tend to implement everything in the most simple way. Both not very good for performance. Never mind that most frameworks don't have the same level of support for every DB (open source libraries tend to have very limited Oracle/SQL Server support) And this is only talking about queries, once we get to triggers, constraints or even stored procedures…