DOWNLOAD THE CODE:
Download the Code 41044.zip

You can test this procedure by running the following code, which executes the procedure against Northwind and msdb:

USE Northwind
EXEC sp_getusertables
EXEC msdb..sp_getusertables

Note that you get different user tables for each database.

SQL Server always resolves special procedures that reference user objects against the master database. For example, first drop any tables called T1 in master, Northwind, and Pubs. Then, run the code that Listing 1 shows to create a table called T1 in the Northwind database and in the Pubs database and a special procedure that returns all rows from T1. Next, run the following code, which executes your procedure first in Northwind, then in Pubs:

EXEC Northwind..sp_getT1rows
EXEC pubs..sp_getT1rows

You get error messages stating that the object name T1 is invalid because SQL Server looks for the table only in master, as the following messages show:

Server: Msg 208, Level 16, 
State 1, Procedure sp_getT1rows, Line 4
Invalid object name 'T1'.
Server: Msg 208, Level 16, State 1, Procedure sp_getT1rows, Line 4
Invalid object name 'T1'.

Apparently, a back door lets you force SQL Server to resolve user objects the same as it does system objects—namely, in the context of the database you're connected to or the one you specify, if you do so explicitly. You mark the procedure as a system object by using the undocumented stored procedure sp_MS_marksystemobject:

USE master
EXEC sp_MS_marksystemobject sp_getT1rows
Now run the previous code snippet again:
EXEC Northwind..sp_getT1rows
EXEC pubs..sp_getT1rows
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Reader Comments

This article disappointed in the beginning but I found the last two pages pretty interesting and useful - thanks.

Cedric (since SQL Server 1.0A so not always in touch with the latest back door potential)

Cedric

Hi,

I found the article interesting, however, I cannot get the code samples to work.

In listing 4 the code

CREATE PROC sp_distinctcount @table_name AS SYSNAME, @col_name AS SYSNAME, @cnt AS OUTPUT

doesn't appear to define as datatype for @cnt and the syntax appears incomplete. I might be incoorect be I was expecting @cnt int OUTPUT.

Upon trying to execute

DECLARE @n AS int EXEC sp_distinctcount @table_name='authors', @col_name='au_lname', @cnt=@n OUTPUT PRINT 'Distinct count of last names of authors is: ' + CAST(@n AS varchar(10))

The error

Server: Msg 214, Level 16, State 2, Procedure sp_executesql, Line 9 Procedure expects parameter '@statement' of type 'ntext/nchar/nvarchar'

was returned.

Could you provide some assistance.

Regards

John Langley

john Langley

Itzik, Excellent article, not just saying it because I respect your knowledge and understanding of SQL Server, I found the information U had to share on special views and tables very useful. . . .I have to admit I stumbled across the executing a special procedure against any database some years ago, and I have found it very useful ever since

Olu Adedeji

Very intresting article. Thanks,Rimon.

Rimon

Script in listing 2 misses nvavchar in declare clause:

CREATE PROC sp_getcolumn @table_name AS SYSNAME, @col_name AS SYSNAME AS DECLARE @sql AS nvarchar (1000) -- here ....

MIkhail

Fix your script, guys Listing 4: Creation Script for the Sp_distinctcount Stored Procedure USE master GO

CREATE PROC sp_distinctcount @table_name AS SYSNAME, @col_name AS SYSNAME, @cnt AS INT OUTPUT -- here AS DECLARE @sql AS nvarchar (1000) SET @sql = N'SELECT @distinctcount = COUNT(DISTINCT [' + @col_name + N']) FROM [' + @table_name + N']'

EXEC sp_executesql @stmt = @sql, @params = N'@distinctcount int OUTPUT', -- here @distinctcount = @cnt OUTPUT GO

Mikhail

You wrote "T-SQL programmers can also use sp_executesql's undocumented output parameters.", but output parameters in sp_executesql are not undocumented. They are documented in KB262499: http://support.microsoft.com/?id=262499

Razvan Socol

Excelent article.

However, the arguments described for sp_execdirect are incorrect. The correct arguments for sp_execresultset are an nvarchar string containing the query and a bit field indicating if debug info needs to be show, instead of executing the resultset. The debug argument has a default of 0 (no debug info).

Karl Gram

When I run EXEC master..xp_execresultset with the accompaning query I get "The command(s) completed successfully." but no records. I have tried both with your example and my own. I am running everything from query analyzer.

(SQL2000)

Mark Murray

I'm trying to use the output parameters for sp_executesql you mentioned in your article, with no success. Here is the code:

ALTER PROCEDURE ap_GetRemoteServerVersion @ServerName varchar(50), @Results nvarchar(65) OUTPUT AS BEGIN DECLARE @SQL nvarchar(500)

SET @SQL = N'exec ' + @ServerName + '.master.dbo.xp_msver ProductVersion'

EXECUTE sp_executesql @Stmt = @SQL, @Params = N'@Results nvarchar(65) OUTPUT', @Results = @Results OUTPUT

END

This is the error message I receive when I run this code:

Procedure 'ap_GetRemoteServerVersion' expects parameter '@Results', which was not supplied.

My purpose in running this code is to capture "Character_Value" from the result set of xp_msver. This value is the SQL Server version information for a particular SQL Server. If you can tell me what I'm doing wrong, or know of another way to capture values from extended stored procedures, it would be greatly appreciated.

Result set for exec xp_msver 'ProductVersion':

Index Name Internal_Value Character_Value ----- -------------- -------------- --------------- 2 ProductVersion 458752 7.00.1063

Ken Powers

Hello Itzik,

Of course you are aware that there is a XP and SP version of ExecResultset. The SP version does not have the TargetDatabase as a parameter. But, your other backdoor trick of calling it from another database even though it lives in Master applies again. These different calls to generate record counts for all tables in pubs give the same result:

master..xp_ExecResultset N'select ''select count(*) as '' + quotename(name) + '' from '' + name from sysobjects where type = ''u'' order by name', N'pubs' go pubs..sp_ExecResultset N'select ''select count(*) as '' + quotename(name) + '' from '' + name from sysobjects where type = ''u'' order by name', 1 go

The code of the SP version can simply be retrieved with sp_helptext SP_ExecResultset (it's extremely ugly).

Thanks, Jacques Roumimper

Jacques Roumimper

the code sp_distinctcount contains the following errors: 1) @CNT AS INT OUTPUT 2) DECLARE @SQL AS NVARCHAR(1000)

michele

Hello Itzik, I used xp_execresultset to execute code. My intention was to execute code longer than 4000 characters. But the procedure truncates the code at 4000 characters. This means that it is not possible to execute code longer than 4000 characters with your method.

However, I did find a solution to execute code longer than 4000 characters. You have to write the code to a text file with BCP and run this text file with te osql command.

Clemens van der Veen.

cvdv

Article Rating 3 out of 5

 
 

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