Interview With Craig Freedman About Indexing, Query Plans And Performance

I interviewed Craig Freedman about Indexing, Query Plans And Performance and more. You can find that interview here: Interview With Craig Freedman About Indexing, Query Plans And Performance

Enjoy

I have a question for you on DB development blunders!

Last week Kalen Delaney wrote Did You Know? I have a question for you on DBA Blunders! I though the comments were very interesting, S we did the DBA part but what about developers? What are some of the worst blunders you have seen?

Here are a couple of things

Starting a begin tran, then some insert/update command, never commiting but minimizing the window.


Here is my all time favorite, can you reduce this by 90%?


declare @Token int
select @Token = 51234567

declare @val int


if left(@Token,1) = 1
select @val = 1
else if left(@Token,1) = 2
select @val = 2
else if left(@Token,1) = 3
select @val = 3
else if left(@Token,1) = 4
select @val = 4
else if left(@Token,1) = 5
select @val = 5
else if left(@Token,1) = 6
select @val = 6
else if left(@Token,1) = 7
select @val = 7
else if left(@Token,1) = 8
select @val = 8
else if left(@Token,1) = 9
select @val = 9
else if left(@Token,1) = 0
select @val = 0


select @val


Actually we put that on the whiteboard after we found it in our code and every time the developer wanted something we teased him about it...Oh you mean like that (pointing to the whiteboard)


What about changing the datatype from smallint to int in the table but keeping the params smallint in the proc.....mmmm why do I get a conversion in the execution plan?





So let's here some of what you have seen others write, we all know we couldn't write stuff like that ourselves right? :-)

Spring Cleaning, Getting Rid Of Some Books

I did some spring cleaning yesterday, I got rid of some old or obsolete books. I asked some people at work if they want any of these books and I believe all the books except for the JCL book are about to be given away.

I got rid of these books because:
I got a new version
I don't use the technology anymore
The book is obsolete


Click on the image and you can see a bigger version on my flickr page.

SSMS Tools PACK 1.0 is now available

Mladen Prajdić just released SSMS Tools PACK 1.0. SSMS Tools PACK is an Add-In (Add-On) for Microsoft SQL Server Management Studio and Microsoft SQL Server Management Studio Express.

Here are some of the features

Uppercase/Lowercase keywords.
Run one script on multiple databases.
Copy execution plan bitmaps to clipboard.
Search Results in Grid Mode and Execution Plans.
Generate Insert statements for a single table, the whole database or current resultsets in grids.
Query Execution History (Soft Source Control).
Text document Regions and Debug sections.
Running custom scripts from Object explorer's Context menu.
CRUD (Create, Read, Update, Delete) stored procedure generation.
New query template.

Check it out here: http://www.ssmstoolspack.com/Main.aspx

How to log when a function is called?

This question came up today and here is one way of doing it. It requires running xp_cmdshell so this is probably not such a good idea.
The problem with functions is that you cannot just insert into any table. INSERT, UPDATE, and DELETE statements modifying table variables local to the function.
EXECUTE statements calling an extended stored procedures are allowed.
So with this in mind we know that we can call xp_cmdshell, from xp_cmdshell we can use osql
Let's take a look
We will be using tempdb


--Create the table
USE tempdb
go
CREATE TABLE LogMeNow (SomeValue varchar(50), SomeDate datetime default getdate())
go

--Here is the proc
CREATE PROC prLog
@SomeValue varchar(50)
AS
INSERT LogMeNow (SomeValue) VALUES(@SomeValue)
go

--And here is the function
CREATE FUNCTION fnBla(@id int)
RETURNS int
AS
BEGIN
DECLARE @SQL varchar(500)
SELECT @SQL = 'osql -S' +@@servername +' -E -q "exec tempdb..prLog ''fnBla''"'
EXEC master..xp_cmdshell @SQL
RETURN @id
END

Now call the function a couple of times

SELECT dbo.fnBla(1)
SELECT dbo.fnBla(2)
SELECT dbo.fnBla(4)

And look inside the table

SELECT * FROM LogMeNow

What if you were to run this?

SELECT dbo.fnBla(4),* FROM sys.sysobjects

See the problem? The function will be called for every row, if you have a big table this can be problematic!!!!!!!!

I tested this on SQL 2000 and on SQL 2005(including a named instance). So there you have it, this is one way. does it smell kludgy and do I feel somewhat dirty now? yes it does indeed :-(

SQL Teaser: @@ROWCOUNT

Without running this what do you think will be printed?


SET ROWCOUNT 0
DECLARE @ int
SET @ =6
IF @@ROWCOUNT = 1
PRINT 'yes'
ELSE
PRINT 'no'
PRINT @@rowcount

Should SQLServer Have The CREATE [OR REPLACE] PROCEDURE Syntax?

I was asked by a developer at work the other day why SQL Server does not have the create or replace syntax. I started thinking and there were some advantages and one big disadvantage

First the advantages

Advantage
When scripting out a database you don’t have to generate if exists.....drop statements

When modifying an object from a file in source control you don’t have to change back and forth between CREATE and ALTER. This is really annoying sometimes; usually you create a proc or script out a proc and store it in Subversion/SourceSafe. Now you take that file, make some changes to the proc and run it. Of course it will tell you that the proc already exists, in general you don’t want to drop the proc and then execute the CREATE proc statement because then you have to worry about the permissions.(not everyone is running as dbo you know)

Disadvantage
I can overwrite a proc without even knowing it. What if we both are working on a proc and somehow we pic the same name I create my proc, you work in a remote location, you create yours and mine is gone.

Of course it is all what you are used to, I am sure the Oracle guys are not overwriting each other’s procs every day either

So what do you think? Would you be in favor of this syntax or not? Can you think of more advantages or disadvantages?

What Would You Like To Ask Erland Sommarskog?

In the Who do you want to see interviewed next?(sqlblog) and Who do you want to see interviewed next?(here) blog post I asked for some names of people who YOU would like to see interviewed. Erland Sommarskog's name was submitted in comments a couple of times. I contacted Erland and am happy to anounce that he has agreed to do this.

The first time I heard of Erland Sommarskog was in the SQL Server programming newsgroups. I also read all the articles on his site. When I answer questions I usually give the link out to these 4 articles
Arrays and Lists in SQL Server
Implementing Error Handling with Stored Procedures
Error Handling in SQL Server – a Background
and of course The curse and blessings of dynamic SQL

I always wondered why he didn't write a SQL book. Hey, now I can ask him that :-)

Before you think of any questions please visit Erland's page first (http://www.sommarskog.se/index.html) and read some of the articles he wrote.

You can submit questions until Monday May 12th and then I will forward the questions to Erland.

What Would You Like To Ask Craig Freedman?

In the Who do you want to see interviewed next?(sqlblog) and Who do you want to see interviewed next?(here) blog post I asked for some names of people who YOU would like to see interviewed. Craig Freedman's name was submitted in comments a couple of times. I contacted Craig and am happy to anounce that he has agreed to do this.

Before you think of any questions please visit Craig's blog first(http://blogs.msdn.com/craigfr/) to get a feel of what kind of questions to ask. It would make sense to keep the questions focused on query processing, query execution, and query plans. I told Craig that if he doesn't like a question that he does not have to answer it.

You can submit questions until Monday May 12th and then I will forward the questions to Craig

Do you depend on sp_depends (no pun intended)

HTML Source EditorWord wrap I answered this question on the MSDN forums: How can I search all my sprocs to see if any use a function?
Several people suggested using sp_depends. You can't really depend on sp_depends because of deferred name resolution. Take a look at this

First create this proc

CREATE PROC SomeTestProc
AS
SELECT dbo.somefuction(1)
GO


now create this function

CREATE FUNCTION somefuction(@id int)
RETURNS int
AS
BEGIN
SELECT @id = 1
RETURN @id
END
Go


now run this


sp_depends 'somefuction'

result: Object does not reference any object, and no objects reference it.



Most people will not create a proc before they have created the function. So when does this behavior rear its ugly head? When you script out all the objects in a database, if the function or any objects referenced by an object are created after the object that references them then sp_depends won't be 100% correct

SQL Server 2005 makes it pretty easy to do it yourself

SELECT

specific_name,*

FROM information_schema.routines

WHERE

object_definition(object_id(specific_name)) LIKE '%somefuction%'

AND

routine_type = 'procedure'

BTW somefuction is not a type, I already had a somefunction but was too lazy to change more than one character

Testing for SQL Server Vulnerabilities

I found this SQL Server Testing (not unit but vulnerability) page and decided I would post a link to it since it has some useful stuff. The link is below

http://www.owasp.org/index.php/Testing_for_SQL_Server

Here is what is covered. Enjoy (or live in fear over the weekend)


1 Brief Summary
2 Short Description of the Issue
3 Black Box testing and example
3.1 SQL Server Peculiarities
3.2 Example 1: Testing for SQL Injection in a GET request.
3.3 Example 2: Testing for SQL Injection in a GET request (2).
3.4 Example 3: Testing in a POST request
3.5 Example 4: Yet another (useful) GET example
3.6 Example 5: custom xp_cmdshell
3.7 Example 6: Referer / User-Agent
3.8 Example 7: SQL Server as a port scanner
3.9 Example 8: Upload of executables
3.10 Obtain information when it is not displayed (Out of band)
3.11 Blind SQL injection attacks
3.11.1 Trial and error
3.11.2 In case more than one error message is displayed
3.11.3 Timing attacks
3.11.4 Checking for version and vulnerabilities
3.12 Example 9: bruteforce of sysadmin password
4 References

Who do you want to see interviewed next?

I have interviewed a bunch of people already, some of them on this blog and some of them on SQLBlog

Below is the list of all the people so far

Louis Davidson
Itzik Ben-Gan
Ken Henderson
Kalen Delaney
Adam Machanic
Interview With Stéphane Faroult About Refactoring SQL Applications
Database Refactoring Interview With Scott W. Ambler
Interview With Joe Celko About The Forthcoming Book Thinking In Sets

Who else should I interview? I have some ideas but I would like you to participate. Here is my thinking, after we have a list of possible people, I will contact them and ask if they will agree to an interview. If they agree I will make a post here and ask you what you would like to ask this person. I usually have a good set of questions but there might be someone out there with some real good/interesting questions.
So post the name of the person you would like to see interviewed and hopefully this person will agree.

It would be nice if you did not pick a person who blogs at SQLBlog but if_you_really_wanted_to then I will not stop you :-0

Please keep it database related, it doesn't have to be specific to SQL Server but it has to be applicable to SQL Server.

SQL Teaser: Some Things Are Not What They Seem

This one is a little sneaky, don’t send me hate mail for it.

What does this return?



SELECT ISNUMERIC('+'),ISNUMERIC('–')

Copy and paste it into QA/SSMS to verify :-0

How to rename a column in a SQL Server table without using the designer

If you have a table and you want to rename a column without using the designer, how can you do that?

First create this table

CREATE TABLE TestColumnChange(id int)
INSERT TestColumnChange VALUES(1)


SELECT * FROM TestColumnChange

As you can see the select statement returns id as the column name. you can use ALTER table ALTER Column to change the dataype of a column but not the name.

Here is what we will do, execute the statement below

EXEC sp_rename 'TestColumnChange.[id]', 'value', 'COLUMN'


Now do the select, you will see that the column name has changed

SELECT * FROM TestColumnChange

That is it, very simple

Interview With Stéphane Faroult About Refactoring SQL Applications

I decided to interview Stéphane Faroult, the author of The Art of SQL because it is one of my favorite SQL books. Stéphane told me he has a new book coming out soon, the name of this book is Refactoring SQL Applications and the majority of this interview is focused on that book.

You can find that interview here: Interview With Stéphane Faroult About Refactoring SQL Applications

Solutions for Common T-SQL Problems Wiki Launched

Volunteer Moderators and Answerers who support the Microsoft MSDN SQL Server Forums have launched a Wiki with Solutions for Common T-SQL Problems. Check it out here: http://code.msdn.microsoft.com/SQLExamples

Use IDENT_CURRENT() to return the last identity value generated in all tables in a SQL Server Database

This is how you return all the tables with their last generated identity values in a SQL Server Database

SELECT IDENT_CURRENT(table_name),*
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_TYPE = 'base table'
AND OBJECTPROPERTY(OBJECT_ID(table_name),'TableHasIdentity')=1

Links Of The Week 20080414

Here are the links for this week

Database

SQL Server 2005 Memory Limits and Related Questions
Microsoft to Increase Use of SQL Server 2005 Best Practices Analyzer (SQLPBA) - So Should You
SqlClient, System.Transactions, SQL Server 2008, and MARS
Visual Linq query builder for Linq to Sql
Converting an EAV design to sparse columns and populating
How It Works: SQL Server Page Allocations
How It Works: File Streams Requires Integrated Security (Windows Authentication)
Troubleshooting xp_cmdshell failures
How It Works: SQL Server Checkpoint (FlushCache) Outstanding I/O Target

Non DB tech

CSS Message Box collection
WCF: Reliable Messaging and Retry Timeouts
Google Starts to Index the Invisible Web
Download YouTube Videos as MP4 Files
New WCF Adapter Code Samples on MSDN!
IUpdatable & ADO.NET Data Services Framework
.NET Rocks! #332 - Ted Neward on the New Language Renaissance

Non tech

Why 24 hours in a Day?
The Publishing Industry Takes Another Hit
What job ads really mean
It's A Dog, Not A Towel (Pics.)
I've got your Highlander right here! [Pic]

Video: SQL Server Data Services Architecture

SQL Server Technical Evangelist Ryan Dunn sits down and talks turkey with two of the creators of SQL Server Data Services (SSDS), Architect Istvan Cseri and Development Manager Nigel Ellis. Istvan and Nigel dig into how to design applications for SSDS and cover a number of the interesting aspects of working with SSDS in terms of features, design, and security.

Watch it here: http://channel9.msdn.com/ShowPost.aspx?PostID=395843#395843

Links Of The Week 20080405

Here are the links for this week

Database
Send Table or View as embedded HTML in an email – stored procedure
How It Works: SQL Server 2005 DBCC Shrink* May Take Longer Than SQL Server 2000
How It Works: Non-Yielding Resource Monitor
Overhead of Row Versioning
TempDB:: Table variable vs local temporary table
sp_helpindex2 to show included columns (2005+) and filtered indexes (2008) which are not shown by sp_helpindex
Yet Another Stored Procedure vs. Ad-hoc Query Discussion?
Geek City: How SQL Server Detects the Correct Versioned Rows
SQLIOSim is "NOT" an I/O Performance Tuning Tool
Forensic Analysis of a SQL Server 2005 Database Server

Non DB tech
Microsoft Live Search Gains Market Share
Unit Testing with Silverlight
Using Spring.NET and NHibernate with ASP.NET MVC
Enterprise Library 4.0 Community Technology Preview
Hanselminutes Podcast 107 - Digital Photography Explained (for Geeks) with Aaron Hockley
How do Extension Methods work and why was a new CLR not required?
Core War: Two Programs Enter, One Program Leaves
How to set an IIS Application or AppPool to use ASP.NET 3.5 rather than 2.0
Let That Be a Lesson To You, Son: Never Upgrade.
Silverlight 2 DIGG Sample Part I
Silverlight 2 DIGG Sample Part II
Silverlight 2 DIGG Sample Part III
Google Developer Podcast: Picasa Web and Google Gears for Mobile
Ted Neward: On Java and .NET, Software Academics versus Practioners, General Purpose Programming Languages
Whirlwind 7: What's New in C# 3 - Lambda Expressions
Google To Launch BigTable As Web Service To Compete With Amazon's SimpleDB

Non tech
SMCB: Charles Manson Pulls a Radiohead
Possibly the best name ever.
Thank God for Torrents (Pic)