Regarding the purpose of database schema

Question

I read a write up about database schema.

A SQL Server schema is a container of objects. For example you may have a large enterprise application and then is a good practice to use different schemas for different purposes (e.g. put HR related tables into HR schema, accounting related tables into Accounting schema and so on). A schema can be owned by any user, and the ownership is transferable.

They said: use different schemas for different purposes (e.g. put HR related tables into HR schema, accounting related tables into Accounting schema and so on)

Do they mean create new database for HR and again new database for accounting?

Because when we create a database then a single schema is created so we cannot create multiple schema in single SQL Server database as far I know.

So please tell me how is it possible to create different schemas for different purposes in a single database? Thanks

Answer 1

Purpose of Schema

Schemas in sql server were introduced in sql server 2005, The main purpose was to eliminate User's ownership of objects in sql server. or you can say to separate users from objects in sql server.

Prior to Sql server 2005 objects in sql server (Tables, views, Store proceders etc) were owned by users. Typically the user who created it.

And that user had to give permissions to other users to use that particular object.

Imagine a scenario where 12 developers are working in a company and all developers are creating sql objects left, right centre. Now all the developers had to give permissions to other 11 developers if they had to work objects created by that one developer. quite a bit of mess isnt it??

Since sql server 2005 came with Schema. All the objects were Owned by a Schema Not a User. if you havent created any custom schema it will be under default Schema dbo.

Now anyone who has permission to dbo schema has permission to any object under dbo schema.

Why it is a good idea to create different schemas for different departments in your case. It may be because HR people doesnt need to know anything about Finance stuff. so you can create a HR schema and give HR people permission only on HR schema. and vice versa with finance people. That will restrict their access to only objects related to their departments.

And we can create multiple Schemas in one database if you have ever worked with Adventureworks database, it has Schemas like 'Production', 'Sales' etc etc.

Read here to learn more about schemas in sql server.

Answer 2

No they mean create a schema. Create schema works within a database. There are all sorts of uses for it, I tend to think of it as either namespacing or a more natural way of partitioning a smallish database and keeping role based access, where you can think of schema as a user group.

Answer 3

Unfortunately, there are two meanings to the word "schema" in the database world.

One means the overall design of the database tables. "Show me your database schema", for example. This would be the collection of "create table" commands, or and ERD diagram.

The other is a synonym for "namespace", which the article in question is referring to. You can store tables, functions etc in different namespaces to ease cognitive load or use for security grouping.