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Deny Permissions on an XML Schema Collection

Permission can be denied to either create a new XML schema collection or use an existing one.

You can deny permission to create an XML schema collection in the following ways:

  • Deny ALTER permission on the relational schema.

  • Deny CONTROL on the relational schema to deny all permissions on the relational schema and on all the contained objects.

  • Deny ALTER ANY SCHEMA on the database. In this case, the principal cannot create an XML schema collection anywhere in the database. Note also that denying ALTER or CONTROL permission on the database denies all permissions on all objects in the database.

Following are the permission that can be denied on an existing XML schema collection and the results:

  • Denying the ALTER permission denies the principal the ability to modify the contents of the XML schema collection.

  • Denying the CONTROL permission denies the principal the ability to perform any operation on the XML schema collection.

  • Denying the REFERENCES permission denies the principal the ability to type or constrain xml type columns and parameters using the XML schema collection. It also denies the principal the ability to refer to this XML schema collection from other XML schema collections.

  • Denying the VIEW DEFINITION permission denies the principal the ability to view the contents of an XML schema collection.

  • Denying the EXECUTE permission denies the principal the ability to insert or update the values in columns, variables, and parameters that are typed or constrained by the XML schema collection. It also denies the principal the ability to query the values in those same xml type columns and variables.

The scenarios in the following examples show how XML schema permissions work. Each example creates the necessary test database, relational schemas, and logins. These logins are granted the necessary XML schema collection permissions. Each example does the necessary cleanup at the end.

A. Preventing a user from creating an XML schema collection

One of the ways to prevent a user from creating an XML schema collection is by denying the ALTER permission on a relational schema. This is shown in the following example.

The example creates a user, TestLogin1, and a database. It also creates a relational schema, in addition to the dbo schema, in the database. Initially, the CREATE XML SCHEMA permission allows the user to create a schema collection anywhere in the database. The example then denies ALTER permission to the user on one of the relational schemas. This prevents the user from creating an XML schema collection in that relational schema.

CREATE LOGIN TestLogin1 WITH password='SQLSvrPwd1'
GO
CREATE DATABASE SampleDBForSchemaPermissions
GO
USE SampleDBForSchemaPermissions
GO
-- Create another relational schema in the database.
CREATE SCHEMA myOtherDBSchema
GO
CREATE USER TestLogin1
GO
-- For TestLogin1 to create/import XML schema collection, following
-- permission needed.
-- Database-level permissions
GRANT CREATE XML SCHEMA COLLECTION TO TestLogin1
GO
GRANT ALTER ANY SCHEMA TO TestLogin1
GO
-- Now TestLogin1 can import an XML schema collection.
SETUSER 'TestLogin1'
GO
CREATE XML SCHEMA COLLECTION myOtherDBSchema.myTestSchemaCollection AS '<?xml version="1.0" encoding="UTF-8" ?>
<xsd:schema targetNamespace="http://schemas.adventure-works.com/Additional/ContactInfo" 
            xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
elementFormDefault="qualified">
<xsd:element name="telephone" type="xsd:string" />
</xsd:schema>'
GO
DROP XML SCHEMA COLLECTION myOtherDBSchema.myTestSchemaCollection
GO
-- Now deny permission from TestLogin1 to alter myOtherDBSchema.
setuser
GO
DENY ALTER ON SCHEMA::myOtherDBSchema TO TestLogin1
GO
-- Now TestLogin1 cannot create xml schema collection.
SETUSER 'TestLogin1'
GO
CREATE XML SCHEMA COLLECTION myOtherDBSchema.myTestSchemaCollection AS '<?xml version="1.0" encoding="UTF-8" ?>
<xsd:schema targetNamespace="http://schemas.adventure-works.com/Additional/ContactInfo" 
            xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
elementFormDefault="qualified">
<xsd:element name="telephone" type="xsd:string" />
</xsd:schema>'
GO
-- Final cleanup
SETUSER
GO
USE master
GO
DROP DATABASE SampleDBForSchemaPermissions
GO
DROP LOGIN TestLogin1
GO

B. Denying permissions on an XML schema collection

The following example shows how a specific permission on an existing XML schema collection can be denied to a login. In this example, a test login is denied REFERENCES permission on an existing XML schema collection.

The example creates a user, TestLogin1, and a database. It also creates a relational schema, in addition to the dbo schema, in the database. Initially, the CREATE XML SCHEMA permission allows the user to create a schema collection anywhere in the database.

The REFERENCES permission on the XML schema collection lets TestLogin1 use the schema in creating a typed xml column in a table. If the REFERENCES permission on the XML schema collection is denied, it prevents the TestLogin1 from using the XML schema collection.

CREATE LOGIN TestLogin1 WITH password='SQLSvrPwd1'
GO
CREATE DATABASE SampleDBForSchemaPermissions
GO
USE SampleDBForSchemaPermissions
GO
-- Create another relational schema in the database.
CREATE SCHEMA myOtherDBSchema
GO
CREATE USER TestLogin1
GO
-- For TestLogin1 to create/import XML schema collection, the following
-- permission is required.
-- Database-level permissions
GRANT CREATE XML SCHEMA COLLECTION TO TestLogin1
GO
GRANT ALTER ANY SCHEMA TO TestLogin1
GO
-- Now TestLogin1 can import an XML schema collection.
SETUSER 'TestLogin1'
GO
CREATE XML SCHEMA COLLECTION myOtherDBSchema.myTestSchemaCollection AS '<?xml version="1.0" encoding="UTF-8" ?>
<xsd:schema targetNamespace="http://schemas.adventure-works.com/Additional/ContactInfo" 
            xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
elementFormDefault="qualified">
<xsd:element name="telephone" type="xsd:string" />
</xsd:schema>'
GO
-- Grant permission to TestLogin1 to create a table and reference the XML schema collection.
SETUSER
GO
GRANT CREATE TABLE TO TestLogin1
GO
-- The user also needs REFERENCES permission to use the XML schema collection
-- to create a typed XML column (REFERENCES permission on the schema 
-- collection is not needed).
GRANT REFERENCES ON XML SCHEMA COLLECTION::myOtherDBSchema.myTestSchemaCollection 
TO TestLogin1
GO

--TestLogin1 can use the schema.
CREATE TABLE T(i int, x xml (myOtherDBSchema.myTestSchemaCollection))
GO
-- Drop the table.
DROP TABLE T
GO
-- Now deny REFERENCES permission to TestLogin1 on the schema created previously.
SETUSER
GO
DENY REFERENCES ON XML SCHEMA COLLECTION::myOtherDBSchema.myTestSchemaCollection TO TestLogin1

GO
-- Now TestLogin1 cannot create xml schema collection
SETUSER 'TestLogin1'
GO
-- Following statement fails. TestLogin1 does not have REFERENCES 
-- permission on the XML schema collection.
CREATE TABLE T(i int, x xml (myOtherDBSchema.myTestSchemaCollection))
GO

-- Final cleanup
SETUSER
GO
USE master
GO
DROP DATABASE SampleDBForSchemaPermissions
GO
DROP LOGIN TestLogin1
GO
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