SQL Server's permissions system recognizes four types of users: the SA, database owners, database object owners, and other users of the database.
The different types of users exist in a hierarchy (explained in the following sections and illustrated below).
Only the SA and database owners can grant statement permissions to other users.
The SA is recognized by SQL Server as a "superuser" who works outside SQL Server's permissions system. The SA is not necessarily an individual user but, rather, is a role in SQL Server.
For more information, choose one of the following topics:
Permissions of Database Owners
Permissions of Database Object Owners
Permissions on System Procedures