What do you mean by Principals? (with respect to SQL Server)

Principals are entities who can request access on SQL Server Resources on different levels, in other words the entities to whom you can grant Right \permission can be referred to as Principals. Every Principal has a Security Identified also known as SID, SID helps you to uniquely identify each principal. We can arrange them in hierarchy; the scope of their influence depends on two things:

1. Where these principals are defined. The Principals can be defined at Windows, Server and Database level.

2. Whether they are Collective or Indivisible in nature; A Windows group can be referred to as a collective nature principal whereas a normal user is an example of an Indivisible principal which you cannot further divide.

As per the scope there could be three types of principals:

A. Windows Level Principals

1. Domain Login (Windows)

2. Local Login (Windows)

B. SQLServer Level Principals

1. SQLServer Login

C. Database Level Principals

1. Database User

2. Database Role

3. Application Role

Note: Every database includes two entities that appear as users in catalog views: INFORMATION_SCHEMA and sys. These entities are required by SQL Server. They are not principals, and they cannot be modified or dropped.

Happy Learning 🙂

Thanks,
Sarabpreet Singh Anand
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