What Is the Security Model Used in SQL Server 2005 in SQL Server?

SQL Server 2005 uses a very standard security model involves 3 concepts:

• Securables - Entities representing resources that need to be secured. For example, a database table is a securable.
• Principals - Entities representing users that request accesses to resources. For example, a login user is a principal.
• Permissions - Types of accesses associated with securables. Permissions can be granted to or revoked from principals. For example, "Update" is a permission associated a securable, table "R". "Update" on "R" can be granted to a principal, user "U". Now user "U" will get "Update" access on table "R".

In simple terms, a principal answers the security question of "Who are you?"; a securable answers the security question of "What is your target object?"; a permission answers the security question of "You are allowed to perform this action on this target object".

SQL Server 2005 supports multiple securables and multiple principals organized into hierarchical structures as shown in this picture:

(Picture by Microsoft)

⇒Managing Security, Login and User in SQL Server

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