SQL isn’t an object-oriented language. There’s no notion of inheritance. The closest thing that SQL has to objects are views, user-defined functions, and stored procedures. Picture a developer at a software shop; this developer has written a distance calculation algorithm in SQL. Other developers copied this same code for use in their projects. After some time, the original developer finds a small defect in the code he wrote. He updates his code and contacts the other developers so that they can make the modification in their code.
This approach has a few problems; here are three of them: