Working with COM Objects from within T-SQL

Introduction

General concepts

OLE Automation Stored Procedures

• sp_OACreate

• sp_OADestroy

• sp_OAGetProperty

• sp_OASetProperty

• sp_OAMethod

• sp_OAGetErrorInfo

• sp_OAStop

Example: generate script

Literature

Introduction

In this article I want to tell you about how you can work with COM objects from within Transact SQL. You can use OLE Automation Stored Procedures (extended stored procedures with sp_OA prefix) to create a COM object in T-SQL and use that object’s methods and properties.

General concepts

The OLE Automation Stored Procedures, in other words, sp_OA procedures (where OA stands for OLE Automation), allow a connection, through T-SQL commands, to create and use Component Object Model (COM) based objects. These procedures are built into SQL Server as an extended stored procedure.

Each OLE Automation stored procedure returns an integer code that is the HRESULT returned by the underlying OLE Automation operation. If HRESULT is equal to 0, then all is okay, a nonzero HRESULT indicates OLE error (in hexadecimal format).

You can use the sp_displayoaerrorinfo stored procedure to display OLE Automation error information (error description, not only hexadecimal code), when error occurs. This very useful procedure is not installed by default, so you can create it manually from SQL Server Books Online.

See this link for more information (here you can find sp_displayoaerrorinfo stored procedure) “OLE Automation Return Codes and Error Information”:
http://msdn.microsoft.com/library/psdk/sql/8_qd_12_25.htm

OLE Automation Stored Procedures

SQL Server supports seven OLE Automation Stored Procedures:

• sp_OACreate
• sp_OADestroy
• sp_OAGetProperty
• sp_OASetProperty
• sp_OAMethod
• sp_OAGetErrorInfo
• sp_OAStop

You can find the description of these stored procedures below.

sp_OACreate

First of all, you should call sp_OACreate stored procedure to create an instance of the OLE object. You should pass two parameters into sp_OACreate stored procedure: program ID or class ID and variable. The variable will be a reference to the OLE object for the further using by other sp_OA stored procedures.

This is the example (for SQL Server 7.0):

DECLARE @object int
DECLARE @hr int

-- Create an object that points to the SQL Server
EXEC @hr = sp_OACreate 'SQLDMO.SQLServer', @object OUT
IF @hr <> 0
BEGIN
  EXEC sp_displayoaerrorinfo @object, @hr
  RETURN
END

NOTE:If you use SQL Server 6.5, you must write ‘SQLOLE.SQLServer’ instead ‘SQLDMO.SQLServer’.

See this link for more information
“sp_OACreate (T-SQL)”: http://msdn.microsoft.com/library/psdk/sql/sp_oa-oz.htm

sp_OADestroy

This stored procedure can be used to destroy a created OLE object. If you don’t call sp_OADestroy, the created OLE object will be destroyed automatically when the batch completes execution.

This is the example:

-- Destroy the previously created SQL Server object
EXEC @hr = sp_OADestroy @object
IF @hr <> 0
BEGIN
  EXEC sp_displayoaerrorinfo @object, @hr
  RETURN
END

See this link for more information
“sp_OADestroy (T-SQL)”: http://msdn.microsoft.com/library/psdk/sql/sp_oa-oz_1.htm

sp_OAGetProperty

You can use sp_OAGetProperty stored procedure to get a property value of an OLE object.

See this link for more information
“sp_OAGetProperty (T-SQL)”: http://msdn.microsoft.com/library/psdk/sql/sp_oa-oz_3.htm

sp_OASetProperty

You can use sp_OASetProperty stored procedure to set a property of an OLE object to a new value.

See this link for more information
“sp_OASetProperty (T-SQL)”: http://msdn.microsoft.com/library/psdk/sql/sp_oa-oz_5.htm

sp_OAMethod

You can use sp_OAMethod stored procedure to call a method of an OLE object.

This example calls the VerifyConnection method of the previously created SQL Server object:

-- Verify the connection
EXEC @hr = sp_OAMethod @object, 'VerifyConnection', @return OUT
IF @hr <> 0
BEGIN
  EXEC sp_displayoaerrorinfo @object, @hr
  RETURN
END

See this link for more information
“sp_OAMethod (T-SQL)”: http://msdn.microsoft.com/library/psdk/sql/sp_oa-oz_4.htm

sp_OAGetErrorInfo

This stored procedure can be used to display OLE Automation error information, when error occurs, as sp_displayoaerrorinfo stored procedure.

However, easier to use sp_displayoaerrorinfo stored procedure instead of sp_OAGetErrorInfo, because sp_displayoaerrorinfo is a wrapped stored procedure for sp_OAGetErrorInfo.

See this link for more information
“sp_OAGetErrorInfo (T-SQL)”: http://msdn.microsoft.com/library/psdk/sql/sp_oa-oz_2.htm

sp_OAStop

This stored procedure can be used to stop the OLE Automation Stored Procedures execution environment.

The execution environment will automatically restart the next time you call sp_OACreate stored procedure.

See this link for more information
“sp_OAStop (T-SQL)”: http://msdn.microsoft.com/library/psdk/sql/sp_oa-oz_6.htm

Example: generate script

This script will generate script for all tables and all dependent objects for the given database.

You can pass the server name, user name, user password, database name and file name into sp_GenerateScript stored procedure, as in the example below:

EXEC sp_GenerateScript @server = 'Server_Name',
                       @uname = 'User_Name',
                       @pwd = 'Password',
                       @dbname = 'Database_Name',
                       @filename = 'c:File_Name.sql'

You can specify different number of parameters (from zero to five parameters).

• If you not specify server name, then the current server will be used;
• If you not specify database name, then the current database will be used;
• If you use Windows NT Authentication mode, then you should not specify username and password;
• If you not specify user name, but specify password, then the current user name will be used;
• If you not specify password, then password will not be used (for example: username = ‘sa’ and empty password, you can pass only username in this case);
• If you not specify file name, then script will be placed into file script.sql on the drive ‘c:’.

  This stored procedure can be used for learning some general SQL Server features (how to work with OLE objects from the SQL Server, how to use some system functions, how to work with cursors and so on).

  if object_id('sp_GenerateScript') is not null drop proc sp_GenerateScript GO CREATE PROC sp_GenerateScript ( @server varchar(30) = null, @uname varchar(30) = null, @pwd varchar(30) = null, @dbname varchar(30) = null, @filename varchar(200) = 'c:script.sql' ) AS DECLARE @object int DECLARE @hr int DECLARE @return varchar(200) DECLARE @exec_str varchar(200) DECLARE @tbname varchar(30) SET NOCOUNT ON -- Set the server to the local server IF @server is NULL SELECT @server = @@servername -- Set the database to the current database IF @dbname is NULL SELECT @dbname = db_name() -- Create an object that points to the SQL Server EXEC @hr = sp_OACreate 'SQLDMO.SQLServer', @object OUT IF @hr <> 0 BEGIN EXEC sp_displayoaerrorinfo @object, @hr RETURN END -- Connect to the SQL Server IF (@uname is NULL) AND (@pwd is NULL) BEGIN -- Windows NT Authentication mode is used EXEC @hr = sp_OAMethod @object, 'Connect', NULL, @server IF @hr <> 0 BEGIN EXEC sp_displayoaerrorinfo @object, @hr RETURN END END ELSE IF (@uname is NULL) BEGIN -- Set the username to the current user name SELECT @uname = SYSTEM_USER EXEC @hr = sp_OAMethod @object,'Connect',NULL,@server,@uname,@pwd IF @hr <> 0 BEGIN EXEC sp_displayoaerrorinfo @object, @hr RETURN END END ELSE IF (@pwd is NULL) BEGIN EXEC @hr = sp_OAMethod @object, 'Connect', NULL, @server, @uname IF @hr <> 0 BEGIN EXEC sp_displayoaerrorinfo @object, @hr RETURN END END ELSE BEGIN EXEC @hr = sp_OAMethod @object,'Connect',NULL,@server,@uname,@pwd IF @hr <> 0 BEGIN EXEC sp_displayoaerrorinfo @object, @hr RETURN END END -- Verify the connection EXEC @hr = sp_OAMethod @object, 'VerifyConnection', @return OUT IF @hr <> 0 BEGIN EXEC sp_displayoaerrorinfo @object, @hr RETURN END SET @exec_str = "DECLARE script_cursor CURSOR FOR SELECT name FROM " + @dbname + "..sysobjects WHERE type = 'U' ORDER BY Name" EXEC (@exec_str) OPEN script_cursor FETCH NEXT FROM script_cursor INTO @tbname WHILE (@@fetch_status <> -1) BEGIN SET @exec_str = 'Databases("'+ @dbname +'").Tables("' + RTRIM(UPPER(@tbname))+'").Script(74077,"' + @filename +'")' EXEC @hr = sp_OAMethod @object, @exec_str, @return OUT IF @hr <> 0 BEGIN EXEC sp_displayoaerrorinfo @object, @hr RETURN END FETCH NEXT FROM script_cursor INTO @tbname END CLOSE script_cursor DEALLOCATE script_cursor -- Destroy the object EXEC @hr = sp_OADestroy @object IF @hr <> 0 BEGIN EXEC sp_displayoaerrorinfo @object, @hr RETURN END GO

  Literature

  1. SQL Server Books Online

  2. Learning About OLE Automation Stored Procedures
  http://www.sqlmag.com/Articles/Index.cfm?ArticleID=7910

  3. OLE Automation Return Codes and Error Information
  http://msdn.microsoft.com/library/psdk/sql/8_qd_12_25.htm

  4. INF: Protocol Error in TDS Stream Causes Function Sequence Error from OLE Automation SPs
  http://support.microsoft.com/support/kb/articles/Q243/8/99.ASP

  5. OLE Automation Sample Script
  http://msdn.microsoft.com/library/psdk/sql/8_qd_12_28.htm

  6. BUG: Sp_OA Procedures May Produce “Bad Variable Type” or “Type Mismatch” Error
  http://support.microsoft.com/support/kb/articles/Q173/8/48.ASP

  7. PRB: How to Use sp_displayoaerrorinfo in the sp_OA Samples
  http://support.microsoft.com/support/kb/articles/Q151/6/02.asp

  8. INF: Examples of Sp_OA Procedure Use and SQLOLE.Transfer Object
  http://support.microsoft.com/support/kb/articles/Q152/8/01.asp

  9. INF: How Sp_OA Procedures Extension to SQL Server Is Implemented
  http://support.microsoft.com/support/kb/articles/Q180/7/80.ASP

  10.INF: Enabling DLL-Based COM Object Execution Outside SQL Server
  http://support.microsoft.com/support/kb/articles/Q198/8/91.ASP

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