Question

What functions do schemas perform – are they necessary?

Answer 1

In the “Oracle” sense of the word, Schemas are kind of have a dual role:

the are User logins (a schema name is also a user with a password

They are collections of objects (tables, procs, etc) “owned” by the schema and stored in various places

This is distinct from many database architectures (Microsoft and MySQL in particular among popular DBs) that instead store objects in “database” structures that are thus owned by “users,” and then multiple users’ objects can be stored within that database.

So, do you “need” schemas? Yes of course:

You need to have logins to databases

You need to have some logical way to define ownership of an object for a multitude of reasons: logistical (so you can back up groups of specific related items without having to individually name them), security (its far easier to do role-based security on groups of objects than doing individual commands on thousands of objects that are all grouped into one ownership structure), and operational (without ownership structures, how could you ever have two objects of the same name in the same database?)

Its kind of like on a PC: why do you have directories for your files? Why not have everything run in c:\? Well, because it’d be nearly impossible to operate for all the reasons noted above.