Never Say Never » Scripts

DBCC INPUTBUFFER vs fn_get_sql

Seth Phelabaum — Sun, 28 Mar 2010 20:57:56 +0000

Someone asked a question in the forums the other day and I realized it would make a pretty decent blog post to explain the differences in functionality between these two and provide some code for working with them.

Differences

fn_get_sql returns the last *statement* executed, where as DBCC INPUTBUFFER returns the first statement in the batch. See the example below for a better idea of what that means.
fn_get_sql returns a TEXT field containing the statement that ran, DBCC INPUTBUFFER returns only a varchar(255). This is important as you often won’t get the full line here… and unfortunately there’s not a lot you can do about that. To my knowledge, DBCC INPUTBUFFER is still your only means of getting the first statement in the batch, however it returns an nvarchar(4000) in 2005/2008.
fn_get_sql requires a SQL_Handle binary type passed in which has to be pulled out of the sysprocesses table, DBCC INPUTBUFFER only requires the SPID as a parameter.
fn_get_sql will return the actual creation text for an SP(or trigger, etc.) that is executing instead of all the name of the object with the parameters that DBCC INPUTBUFFER returns.

Note that fn_get_sql is available in SQL 2000 if you have sp3 and above. You may actually have it with SP2 as well if you have the correct hotfix applied. An easy way to tell if it will work on your system is to do a simple SELECT sql_handle FROM sysprocesses. If that works, so will fn_get_sql. If it doesn’t, you need to patch. There are a couple other specifics about fn_get_sql that are mentioned in the article linked at the bottom by Andrew Novick.

Sample Code

Both of these often require insertion into a table to work with. Here is some sample code that will create the tables for you and insert the rows of the currently running SPID.

--- Change eventinfo to nvarchar(4000) for sql 2005 and 2008
REATE TABLE #B(eventtype nvarchar(30), parameters INT, eventinfo nvarchar(255))
INSERT INTO #B(EventType, Parameters, EventInfo)
EXEC ('dbcc inputbuffer (' + @@spid + ') with no_infomsgs')

DECLARE @handle BINARY(20)
SELECT @handle = MAX(sql_handle) FROM master..sysprocesses WHERE spid = @@SPID
SELECT * FROM ::fn_get_sql(@handle)

Additional Links:

Andrew Novick: Find out what they’re doing with fn_get_sql
BOL: sys.dm_exec_sql_text
BOL: fn_get_sql
BOL: DBCC INPUTBUFFER: 2008 | 2005 | 2000

Examples:

Here are a couple examples that show some of the differences between the two in action.

USE tempdb
GO

CREATE PROCEDURE Proc1(
@invar        VARCHAR(100)
)
AS

SET NOCOUNT ON

PRINT 'Proc 1 Executing'
DECLARE @fgs    nvarchar(4000),
@handle varbinary(64),
@dbib    nvarchar(4000)
SELECT @handle = MAX(sql_handle) FROM master..sysprocesses WHERE spid = @@SPID

CREATE TABLE #A(eventtype nvarchar(30), parameters INT, eventinfo nvarchar(4000))
INSERT INTO #A(EventType, Parameters, EventInfo)
EXEC ('dbcc inputbuffer (' + @@spid + ') with no_infomsgs')

SELECT @fgs = text FROM ::fn_get_sql(@handle)
SELECT @dbib = eventinfo FROM #A
PRINT 'fn_get_sql'
PRINT '---------------------'
PRINT @FGS
PRINT 'DBCC INPUTBUFFER:'
PRINT '---------------------'
PRINT @dbib

EXEC Proc2 'Executing Second Proc'

GO

CREATE PROCEDURE Proc2(
@invar    VARCHAR(100)
)
AS

SET NOCOUNT ON

PRINT 'Proc 2 Executing'
DECLARE @fgs    nvarchar(4000),
@handle varbinary(64),
@dbib    nvarchar(4000)
SELECT @handle = MAX(sql_handle) FROM master..sysprocesses WHERE spid = @@SPID

CREATE TABLE #B(eventtype nvarchar(30), parameters INT, eventinfo nvarchar(4000))
INSERT INTO #B(EventType, Parameters, EventInfo)
EXEC ('dbcc inputbuffer (' + @@spid + ') with no_infomsgs')

SELECT @fgs = text FROM ::fn_get_sql(@handle)
SELECT @dbib = eventinfo FROM #B
PRINT 'fn_get_sql'
PRINT '---------------------'
PRINT @FGS
PRINT 'DBCC INPUTBUFFER:'
PRINT '---------------------'
PRINT @dbib
EXEC Proc3 'Executing Third Proc'
GO

CREATE PROCEDURE Proc3(
@invar    VARCHAR(100)
)
AS

SET NOCOUNT ON
PRINT 'Proc 3 Executing'
DECLARE @fgs    nvarchar(4000),
@handle varbinary(64),
@dbib    nvarchar(4000)
SELECT @handle = MAX(sql_handle) FROM master..sysprocesses WHERE spid = @@SPID

CREATE TABLE #C(eventtype nvarchar(30), parameters INT, eventinfo nvarchar(4000))
INSERT INTO #C(EventType, Parameters, EventInfo)
EXEC ('dbcc inputbuffer (' + @@spid + ') with no_infomsgs')

SELECT @fgs = text FROM ::fn_get_sql(@handle)
SELECT @dbib = eventinfo FROM #C
PRINT 'fn_get_sql'
PRINT '---------------------'
PRINT @FGS
PRINT 'DBCC INPUTBUFFER:'
PRINT '---------------------'
PRINT @dbib
GO

EXEC Proc1 'Executing Proc 1'
GO

DROP PROCEDURE Proc1
DROP PROCEDURE Proc2
DROP PROCEDURE Proc3
GO

---- Example 2 -----
PRINT '------------------------------- Example 2 ---------------------------------------'
GO

CREATE TABLE A(
aval INT)
GO
CREATE TRIGGER Atrig ON A
FOR INSERT
AS
SET NOCOUNT ON
DECLARE @fgs    nvarchar(4000),
@handle varbinary(64),
@dbib    nvarchar(4000)
SELECT @handle = MAX(sql_handle) FROM master..sysprocesses WHERE spid = @@SPID

CREATE TABLE #C(eventtype nvarchar(30), parameters INT, eventinfo nvarchar(4000))
INSERT INTO #C(EventType, Parameters, EventInfo)
EXEC ('dbcc inputbuffer (' + @@spid + ') with no_infomsgs')

SELECT @fgs = text FROM ::fn_get_sql(@handle)
SELECT @dbib = eventinfo FROM #C
PRINT 'fn_get_sql'
PRINT '---------------------'
PRINT @FGS
PRINT 'DBCC INPUTBUFFER:'
PRINT '---------------------'
PRINT @dbib
GO

INSERT INTO A(aval) SELECT 123456

GO
DROP TABLE A
GO

Tally Table CTE

Seth Phelabaum — Fri, 19 Mar 2010 13:24:48 +0000

Now that I have several posts on what you can do with a Tally table, I figured I’d share my favorite way to create one inline. I still prefer to have a physical tally table (usually in a Utility database that can be accessed from anywhere and doesn’t need to be created in each individual database) for permament code, but for times when you need one on the fly, this is my preferred method. I can’t really take the credit for this query, the base construct is based on something I’ve seen attributed to Itzik Ben-Gan. I’ve modified it a bit and changed up the formatting to be the way I like it. Anything over a few thousand rows I’d probably use a physical tally table for, but on small numbers you shouldn’t see much of a performance hit with this script.

-- Tally Table CTE script (SQL 2005+ only)
-- You can use this to create many different numbers of rows... for example:
-- You could use a 3 way cross join (t3 x, t3 y, t3 z) instead of just 2 way to generate a different number of rows.
-- The # of rows this would generate for each is noted in the X3 comment column below.
-- For most common usage, I find t3 or t4 to be enough, so that is what is coded here.
-- If you use t3 in ‘Tally’, you can delete t4 and t5.

; WITH
-- Tally table Gen            Tally Rows:     X2                X3
t1 AS (SELECT 1 N UNION ALL SELECT 1 N),    -- 4            ,    8
t2 AS (SELECT 1 N FROM t1 x, t1 y),            -- 16            ,    64
t3 AS (SELECT 1 N FROM t2 x, t2 y),            -- 256            ,    4096
t4 AS (SELECT 1 N FROM t3 x, t3 y),            -- 65536        ,    16,777,216
t5 AS (SELECT 1 N FROM t4 x, t4 y),            -- 4,294,967,296,    A lot
Tally AS (SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) N
FROM t3 x, t3 y) -- Change the t3's to one of the other numbers above for more/less rows

Tally Table – Delimited list to Table

Seth Phelabaum — Sat, 27 Feb 2010 20:49:27 +0000

Dealing with delimited lists (Usually separated by a comma) in SQL is a problem easily handled by a simple function and a Tally Table. (Tally tables are also often referred to as Numbers tables or spt_values tables. If you still don’t know what that is, please see this excellent article on Tally tables written by my friend and SSC heavyweight Jeff Moden.) This particular implementation is somewhat specific in nature but can give you an alternative to Dynamic SQL when you want to pass in a list as a parameter and do an IN in a Stored Procedure. The following function will take your delimiter and string and parse it into a table so you can do your IN. (I’m leaving my standard header on the function in this case because there are some good notes in there.)

/*
=============================================================================================
CREATE DATE:     02/27/2010
LAST MODIFIED:    02/27/2010
CREATED BY:        SETH PHELABAUM
PURPOSE:        Splits a string based on a passed in delimiter and returns a table.
ISSUES:            Strings with extra 's will break this function, handle that on the end that calls it.
Notes:            To make it a simpler function, I removed the peice that trimmed spaces around commas. Do
this before or after calling it.
Revision History:
Date     By        Change Made
-------- ---      -------------------------------------
=============================================================================================
GRANT SELECT ON TVF_TallySplit TO [Somebody]
SELECT * FROM TVF_TallySplit(',','Orange,Apple,Banana,Pear,Watermelon,Grape')
SELECT * FROM TVF_TallySplit('*','Orange*Apple*Banana*Pear*Watermelon*Grape')
DROP FUNCTION TVF_TallySplit
*/

CREATE FUNCTION TVF_TallySplit(
@Delim            CHAR(1),            -- List Delimiter
@String            VARCHAR(8000))
RETURNS TABLE
AS

RETURN(
SELECT SUBSTRING(@Delim + @String + @Delim,N+1,CHARINDEX(@Delim,@Delim + @String + @Delim,N+1)-N-1) ListValue
FROM Tally
WHERE N < LEN(@Delim + @String + @Delim)
AND SUBSTRING(@Delim + @String + @Delim,N,1) = @Delim )

What to do with this
Let’s say you have a table containing names of your favorite fruits. (In case you were wondering… No, these aren’t my favorite fruits; they were just ones that immediately came to mind when writing this. I don’t even like half of these.)

CREATE TABLE Fruits(
Name VARCHAR(25))

INSERT INTO Fruits(Name)
SELECT 'Apple' UNION ALL SELECT 'Banana' UNION ALL SELECT 'Grapefruit' UNION ALL
SELECT 'Kiwi' UNION ALL SELECT'Tomatoe' UNION ALL SELECT 'Grape' UNION ALL
SELECT 'Orange' UNION ALL SELECT 'DragonFruit' UNION ALL SELECT 'Strawberry'

You then ask someone else what their favorite fruits are and want to see what fruits you have in common. You might think you could just write a query for that like this:

DECLARE @YFFruits VARCHAR(200)

SET @YFFruits = 'Orange,Apple,Banana,Pear,Watermelon,Grape'
-- OR SET @YFFruits = '''Orange'',''Apple'',''Banana'',''Pear'',''Watermelon'',''Grape'''

SELECT * FROM Fruits WHERE Name LIKE (@YFFruits)
-- OR SELECT * FROM Fruits where Name IN (@YFFruits)

However, this won’t work because in all these cases SQL is looking for a single fruit named : ‘Orange,Apple,Banana,Pear,Watermelon,Grape’ not any fruit in what is really a list.

A common solution for this is to use Dynamic SQL which would make your query this:

DECLARE @YFFruits VARCHAR(200)
SET @YFFruits = '''Orange'',''Apple'',''Banana'',''Pear'',''Watermelon'',''Grape'''
EXEC('SELECT * FROM Fruits WHERE Name IN (' + @YFFruits + ')')

This works and will properly match up your fruits.

The above function allows you to accomplish your goal without Dynamic SQL with a query that looks like this:

DECLARE @YFFruits VARCHAR(200)
SET @YFFruits = 'Orange,Apple,Banana,Pear,Watermelon,Grape'
SELECT * FROM Fruits WHERE Name IN (SELECT * FROM Util.dbo.TVF_TallySplit(',',@YFFruits))

You can also simply join to the table instead of using the IN keyword which gives you more flexibility in your query writing.

DECLARE @YFFruits VARCHAR(200)
SET @YFFruits = 'Orange,Apple,Banana,Pear,Watermelon,Grape'
SELECT Fruits.*
FROM Fruits
INNER JOIN Util.dbo.TVF_TallySplit(',',@YFFruits)) T ON Fruits.Name = T.ListValue

Note that because I wanted to keep the function somewhat simple, it does not handle extra spaces around the commas. Single quotes within the string will also break it which limits its usage somewhat. If this is a concern for your implementation, you either need to replace the single quotes on both sides or use a different method. Despite the fact that the example above uses a list of strings, in real life situations I use this mainly for lists of uniqueidentifiers or numbers where single quotes/spaces are never an issue.

Tally Table – String Cleaning

Seth Phelabaum — Wed, 13 Jan 2010 14:37:11 +0000

Overview
This is something that most people eventually need for reporting purposes. This function uses a Tally table to ‘clean’ a string, removing anything you don’t specify in the @Rep parameter. In the case below, I remove everything but letters, numbers, spaces, commas and periods. This is a slightly modified version of a function I wrote for something else, so the specifics like replacing a lot of the double spaces, and replacing carriage returns and line breaks with spaces were specifically for that. Remove those pieces of code if you wish, or add those as additional parameters to the function.

Other Methods
I’ll mention that I’ve seen people claim a while loop will beat this method and others that say this method is still faster. I haven’t tested this enough personally to make the claim one way or another, but I prefer this one. This is also one of the accepted places where a CLR function can be superior to T-SQL, but for people who can’t or don’t want to use CLR on their servers, this will still work.

Tally Method

/*
SELECT dbo.SSC_fn_TallyClean('This will remove all of this---->!)#%*)^+__#@#$+_!)#~!!! <----.','[a-zA-Z0-9. ,]') Cleaned
*/

CREATE FUNCTION SSC_fn_TallyClean(
@A VARCHAR(500),
@Rep VARCHAR(100))
RETURNS VARCHAR(500)

AS
BEGIN
DECLARE @B VARCHAR(500)
SET @B = '' -- Initialize @B

-- Remove Line Feed / Carriage Returns (The tally code would have removed them, but I wanted to replace them with spaces for readability.)
SET @A = REPLACE(REPLACE(@A,CHAR(10),' '),CHAR(13),' ')

SELECT @B = @B + SUBSTRING(@A,N,1)
FROM Tally
WHERE N <= DATALENGTH(@A)
AND SUBSTRING(@A,N,1) LIKE @Rep -- Remove everything but letters, numbers, spaces, period and comma.

RETURN REPLACE(REPLACE(@B,' ',' '),' ',' ') -- Removes some double spaces.
END