TWmiQuery Component For Delphi, C++Builder

TWmiQuery is a part of WmiSet Component Collection for Delphi, C++Builder. This component executes queries against Windows Management Instrumentation (WMI) service of Windows operating system.

SQL for WMI

WMI is a mainstream technology that currently dominates the area of Windows OS management. WMI exposes much wider set of information than it is possible to retrieve via Windows API. WMI utilizes a special query language, called WQL. WQL is a SQL-like language that allows to express queries in text form. For example, to retrieve list of account on a computer, one could issue a query "SELECT * FROM Win32_Account". Find the full description of WQL language on Microsoft Web site. The result of WQL query is a set of WMI objects. These objects are exposed via their COM interfaces that may be used to retrieve properties of objects.

TWmiQuery simplifies development

TWmiQuery VCL component executes WQL queries and exposes properties of retrieved objects as fields. TWmiQuery is a descendant of TDataSet. If you ever developed database applications in Delphi or C++Builder, you already know how to use TWmiQuery. This snippet of Delphi code is familiar to many:

WmiQuery1.WQL.Text := 'SELECT * '+
                      'FROM Win32_LogicalDisk '+
                      'WHERE FreeSpace > 1000000';
WmiQuery1.Active := true;
while not WmiQuery1.EOF do
begin
  //
  // do processing here...
  //
  WmiQuery1.Next;
end;

The component can also update properties of the objects. Please note that most of properties of WMI objects are read-only. WMI does not throw errors if the read-only property is updated. When reloading the objects with read-only properties, the property values will rollback to their old values. Here is the example of changing the description of the local computer:

WmiQry1.WQL.Add('select * from Win32_OperatingSystem');
WmiQry1.ReadOnly := false;
WmiQry1.Open;
WmiQry1.Edit;
WmiQry1.FieldByName('Description').AsString := 
        'Mail Server - Backup';
WmiQry1.Post;

TWmiQuery features/restrictions

Execute regular WQL queries, like "SELECT * FROM Win32_DiskDrive"; Use WQL property.
Connect to network computers via TWmiConnection component; Use Connection property.
Browse retrieved data set. Use Next, Prev, First, Last methods.
Read properties of retrieved WMI objects. For each property in the WMI object the component will create a field with the same name. Use Fields property, FieldByName method.
Retrieve WMI object as a whole. Use CurrentObject property.
Search records in dataset. Use Locate methods.
Work with irregular dataset, where each object in the dataset has different set of properties. Use IrregularView, IrregularFieldDefs, IrregularFieldValues properties.
Declare and jump to bookmarks. Use GetBookmark, GotoBookmark methods.
Change fields of objects with Edit and Post methods.
Key fields are always included in the result set, even when not asked for;
Filtering is not supported.
The returned data set is not ordered. The order may change from query to query.

TWmiQuery Demo

WmiSet component collection comes with demo application that shows how to use TWmiQuery with data controls. You may use this application to test your WQL statements. The application is capable of connecting to computers on the network. This may be useful when testing compatibility with different operating systems. Download WmiSet to see the source code of the demo application. You may also download executable here.

Useful WQL queries

We provide a number of common WQL queries here. You can use these queries as is, or customize then at will. If you need to write a new query but you are not experienced with WQL, contact technical support. We will be happy to help.

WQL

Purpose

SELECT * from Win32_NTLogEvent where Logfile = "Application"	Returns events from event log, section "Application"
SELECT * FROM Win32_Account	Returns all accounts known to the computer. This includes generic accounts, like "Guest" and user accounts
SELECT * FROM Win32_Group	Returns information about all the user groups known to the destination computer
SELECT * FROM Win32_LogicalDisk WHERE FreeSpace > 10000000	Returns list of logical disks with free space greater than 10 Mb.
SELECT * FROM Win32_Service WHERE state = "Running"	Returns list of all running services.
ASSOCIATORS OF {Win32_Group.Domain="domain", Name="user"} WHERE ResultClass = Win32_Group	Lists all the groups that user domain\user is a member of.
ASSOCIATORS OF {Win32_Group.Domain="domain", Name="group"} WHERE ResultClass = Win32_UserAccount	Lists all the users that are members of a group domain\group. Note: if the group that you are interested in contains both user and group accounts, this query becomes extremely slow. Instead you may execute the following query
SELECT * FROM Win32_GroupUser WHERE GroupComponent = "Win32_Group.Domain='domain', Name='group'"	Lists all the users that are members of a group domain\group. Note: This query does not return the WMI objects. Instead, it returns the string references to the destination objects that may be parsed to retrieve the members' names.
SELECT * FROM Win32_DiskPartition WHERE DiskIndex = 0	Lists all the partitions of the first hard drive.
SELECT EstimatedRunTime FROM Win32_Battery	When computer is running on batteries, returns estimated run time, in minutes.
SELECT * from Win32_PhysicalMemory	Returns all the physical memory installed on the computer. This includes RAM, ROM, EPROM etc.
SELECT * FROM Win32_NetworkAdapterConfiguration WHERE IPEnabled = true	Returns information about network adapters, just like ipconfig /all