How to Use DAO to Assign or View Permissions

 Last reviewed: June 20, 1996
Article ID: Q130645
The information in this article applies to:
  • Professional and Enterprise Editions of Microsoft Visual Basic, 16-bit and 32-bit, for Windows, version 4.0

SUMMARY

In Microsoft Visual Basic version 4.0, you can assign permissions to database objects in a program by using data access objects (DAO). This article shows you how.

MORE INFORMATION

Steps to Secure Database

Securing a database involves these steps:

  1. Create group accounts. For information on how to do this, please see the CreateGroup method in the Visual Basic Help menu.

  2. Create user accounts. For information on how to do this, please see the CreateUser method in the Visual Basic Help menu.

  3. Assign users to groups.

  4. Assign permissions on database objects to users and groups. This article describes this step in detail.

  5. Encrypt the database, if desired. For information on how to do this, please see options:dbEncrypt under the CompactDatabase and CreateDatabase methods in the Visual Basic Help menu.

Assigning Permissions on Database Objects to Users and Groups

To assign permissions for an object, you must reference the UserName and Permissions properties of the object's document. All database objects can be treated as documents in a container. For example, suppose you have this DB variable assignment: 

   Dim DB As Database
   Set DB = DBEngine.Workspaces(0).Opendatabase("Biblio.mdb")
A table called Authors can be referred to using DAO as follows: 

   DB.Containers("Tables").Documents("Authors")
However, it is usually easier to assign and work with object variables: 

   Dim DB as Database, DOC as Document
   Set DB = DBEngine.Workspaces(0).OpenDatabase("Biblio.MDB")
   Set DOC = DB.Containers("Tables").Documents("Authors")
You can reference the UserName and Permissions properties of the Table1 document directly by using this code: 

   UserNameVariable = DOC.UserName
   PermissionsVariable = DOC.Permissions

   -or-

   DOC.UserName = "MyUser"
   DOC.Permissions = dbSecFullAccess

Reading Permissions Information

To read the permissions that a given user or group has on an object, set the UserName property of the document to that user or group name, and then read the value of the Permissions property.

NOTE: To use the following examples, you must already have a database with security established. That is, a SYSTEM.MDA file exists.

The following example shows how to read the permissions for the user John on table TestTable: 

   Dim DB as Database, DOC as Document, HisPermissions as Long
   Set DB = DBEngine.Workspaces(0).Opendatabase("Test.MDB")
   Set DOC = DB.Containers("Tables").Documents("TestTable")
   DOC.UserName = "John"
   HisPermissions = DOC.Permissions
NOTE: Whether you inquire about a group or a user, you still set the UserName property. There is no GroupName property for a document.

Assigning Permissions Information

To assign permissions for a user on an object, set the UserName property of the document to the name of the user or group. Then set the Permissions property of the document to the appropriate value.

Generally, you should use the predefined constants when you assign permissions. For a complete list of the predefined constants, search under DAO for constants starting with 'dbSec' in the Object Browser.

The following example shows how to assign Full permissions on the Employees table for a user named Martha: 

   Dim DB as Database, DOC as Document
   Set DB = DBEngine.Workspaces(0).Opendatabase("TestDB.MDB")
   Set DOC = DB.Containers("Tables").Documents("Employees")
   DOC.UserName = "Martha"
   DOC.Permissions = dbSecFullAccess

Additional reference words: 4.00 vb4win vb4all
KBCategory: kbprg kbcode
KBSubcategory: APrgDataOther

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Last reviewed: June 20, 1996
© 1998 Microsoft Corporation. All rights reserved. Terms of Use.