Review of Inside Microsoft SQL Server 2005 Query Tuning and Optimization

SQL performance tuning is probably one of those things you can do to really make a HUGE difference in performance. Let’s put this in perspective: take a typical application, if you can improve the performance by 100% then you really made a huge improvement. You can improve a SQL query by 1000% with 2 lines of code (sometimes all you have to do is take away a % sign). If you can make a query sargable so that the optimizer can do an index seek instead of an index scan your query might go from 12 seconds to 200 milliseconds. Now try doing that in an application, even if you change all the string concatenation to use a stringbuilder instead of creating new strings all the time you will not get such a drastic performance improvement. I am sure you get the point by now, let’s talk about the book.

Inside Microsoft SQL Server 2005: Query Tuning and Optimization is part 4 of the Inside Microsoft SQL Server 2005 series, it is written by Kalen Delaney and five other authors. There are 6 chapters in this book

1 A Performance Troubleshooting Methodology

This chapter explains some typical things that affect performance and also gives a troubleshooting overview


2 Tracing and Profiling

This chapter explains how to use the profiler and how to analyze traces. SQL Server’s built-in traces are also covered


3 Query Execution

This chapter gives a query processing and execution overview. It explains how to read plans and goes into a lot of detail about analyzing plans


4 Troubleshooting Query Performance

This chapter explains how to detect problems in plans, how to improve queries and some best practices


5 Plan Caching and Recompilation

This chapter goes into detail about plan caching and recompilation and how to troubleshoot plan cache issues


6 Concurrency Problems

The final chapter deals with concurrency (locking, blocking and deadlocking)



This is an excellent book for an intermediate/advanced developer. There is so much new stuff in SQL Server 2005 compared to 2000 to help you with tuning queries that you probably want to read each chapter several times. The Dynamic Management Views are a big help and this book shows you how to use them. Some other cool stuff in this book is the discussion of internal tables, undocumented DBCC commands and undocumented trace flags to discover information which could help you determine much faster what the cause of a performance problem might be.
Some pages are packed with so much information that you need to pause for a second and process all that info (I have read some pages two to three times in a row). You will also find out that there are more joins besides left, full and outer. Page 137 for example has a nice table with the three Physical Join Operators: Nested Loop Join, Hash Join and Merge Join. This table lists the characteristics for each of these joins.

If you are an intermediate to advanced developer then I highly recommend this book. I have interviewed Kalen a while back about this book and you can find that interview here
http://sqlservercode.blogspot.com/2007/10/interview-with-kalen-delaney-about.html

33 New Dynamic Management Views In SQL Server 2008

I was just poking around in SQL Server 2008 and wanted to know if there were any new Dynamic Management Views. There are a total of 33 new Dynamic Management Views. The list of them is below, I think their names make clear what the dmv is supposed to do (or at least I think I know)

dm_cdc_errors
dm_cdc_log_scan_sessions
dm_cryptographic_provider_algorithms
dm_cryptographic_provider_keys
dm_cryptographic_provider_properties
dm_cryptographic_provider_sessions
dm_database_encryption_keys
dm_db_mirroring_auto_page_repair
dm_db_mirroring_past_actions
dm_filestream_oob_handles
dm_filestream_oob_requests
dm_os_dispatcher_pools
dm_os_memory_brokers
dm_os_memory_nodes
dm_os_nodes
dm_os_process_memory
dm_os_spinlock_stats
dm_os_sys_memory
dm_resource_governor_configuration
dm_resource_governor_resource_pools
dm_resource_governor_workload_groups
dm_sql_referenced_entities
dm_sql_referencing_entities
dm_tran_commit_table
dm_xe_map_values
dm_xe_object_columns
dm_xe_objects
dm_xe_packages
dm_xe_session_event_actions
dm_xe_session_events
dm_xe_session_object_columns
dm_xe_session_targets
dm_xe_sessions

If you want to find out what the names of all the new DMVs are by running a query on your SQL Server 2008 box and you don't have a linked server to a SQL Server 2005 box then don't worry I have prepared the query below for you.

SELECT * FROM sysobjects
WHERE name LIKE 'dm_%'
AND name NOT IN('dm_os_hosts',
'dm_exec_cached_plan_dependent_objects',
'dm_os_memory_allocations',
'dm_os_loaded_modules',
'dm_db_task_space_usage',
'dm_os_memory_objects',
'dm_os_schedulers',
'dm_os_threads',
'dm_exec_requests',
'dm_db_missing_index_columns',
'dm_repl_tranhash',
'dm_qn_subscriptions',
'dm_db_session_space_usage',
'dm_exec_query_optimizer_info',
'dm_tran_top_version_generators',
'dm_os_waiting_tasks',
'dm_exec_background_job_queue',
'dm_exec_cursors',
'dm_db_missing_index_details',
'dm_clr_properties',
'dm_os_sublatches',
'dm_exec_query_memory_grants',
'dm_tran_current_snapshot',
'dm_io_virtual_file_stats',
'dm_exec_xml_handles',
'dm_os_wait_stats',
'dm_exec_text_query_plan',
'dm_broker_connections',
'dm_os_stacks',
'dm_os_ring_buffers',
'dm_db_missing_index_groups',
'dm_exec_cached_plans',
'dm_exec_sessions',
'dm_broker_forwarded_messages',
'dm_os_memory_clerks',
'dm_repl_articles',
'dm_fts_memory_buffers',
'dm_fts_index_population',
'dm_tran_current_transaction',
'dm_os_child_instances',
'dm_exec_connections',
'dm_exec_background_job_queue_stats',
'dm_fts_active_catalogs',
'dm_tran_database_transactions',
'dm_os_memory_cache_clock_hands',
'dm_repl_schemas',
'dm_db_mirroring_connections',
'dm_db_index_operational_stats',
'dm_db_partition_stats',
'dm_io_pending_io_requests',
'dm_os_memory_cache_entries',
'dm_os_virtual_address_dump',
'dm_tran_transactions_snapshot',
'dm_exec_query_plan',
'dm_os_memory_cache_hash_tables',
'dm_exec_query_stats',
'dm_clr_tasks',
'dm_os_worker_local_storage',
'dm_db_index_usage_stats',
'dm_db_index_physical_stats',
'dm_os_buffer_descriptors',
'dm_tran_active_snapshot_database_transactions',
'dm_tran_active_transactions',
'dm_db_file_space_usage',
'dm_broker_activated_tasks',
'dm_broker_queue_monitors',
'dm_os_memory_cache_counters',
'dm_tran_session_transactions',
'dm_clr_appdomains',
'dm_exec_sql_text',
'dm_os_memory_pools',
'dm_os_latch_stats',
'dm_io_backup_tapes',
'dm_fts_memory_pools',
'dm_os_sys_info',
'dm_tran_locks',
'dm_exec_query_transformation_stats',
'dm_exec_query_resource_semaphores',
'dm_repl_traninfo',
'dm_db_missing_index_group_stats',
'dm_fts_population_ranges',
'dm_os_performance_counters',
'dm_os_workers',
'dm_io_cluster_shared_drives',
'dm_os_tasks',
'dm_exec_plan_attributes',
'dm_tran_version_store',
'dm_os_cluster_nodes',
'dm_clr_loaded_assemblies')

Enjoy exploring these DMVs

Windows Server 2008 and Vista SP1 releasing to manufacturers today

Windows Server 2008 RTM: http://www.microsoft.com/presspass/features/2008/feb08/02-04WS2008.mspx

Windows Vista SP1: http://windowsvistablog.com/blogs/windowsvista/archive/2008/02/04/announcing-the-rtm-of-windows-vista-sp1.aspx

Should You Get Your Database Under Version Control?

CodingHorror has a blogpost titled Get Your Database Under Version Control

It is suggested that you also keep the data in version control. I am reading through the comments and I am amazed. One person writes "Once you have used ActiveRecord Migrations it is very hard to go back!"

This might work for a small or medium size database. My database is well over a terabyte, how would you keep that data under version control? Data gets modified every day. Some of the data is encrypted. Some of the data gets inserted into audit tables. Data gets replicated to other servers/databases. There are jobs that pull in data from real time systems every second. I do have different versions of DBs on staging and QA servers but only one on the production server. Changes have to go through change management, you have to open a ticket to do a change. This is not something you would do on a daily basis.

What is your opinion? Do you have the schema in version control? What about the data itself?

Vote for SQL Server 2005 Service Pack 3

Hugo Kornelis makes a good point here: Want a Service Pack? Ask for it!

Service pack 2 for SQL Server 2005 is already 11 months old. And there is still no sign of service pack 3 on the horizon. Why is that? Has Microsoft managed to release a perfect, completely bug-free product? No, of course not – with the size and complexity of a product such as SQL Server is, that will simply never happen.

So do yourself (and me) a favor and vote here: http://connect.microsoft.com/SQLServer/feedback/ViewFeedback.aspx?FeedbackID=326575

Some Very Sad News For The SQL Server Community

Ken Henderson passed away this last Sunday. My condolences go out to his family, friends, and coworkers. I owe so much to Ken, if it wasn't for his books I would not be where I am today.

Ken, You will be missed.

SQL Server 2008 To RTM In Q3 2008

Francois Ajenstat on his blog writes that

"Microsoft is excited to deliver a feature complete CTP during the Heroes Happen Here launch wave and a release candidate (RC) in Q2 calendar year 2008, with final Release to manufacturing (RTM) of SQL Server 2008 expected in Q3."

You can read the whole blog post here: http://blogs.technet.com/dataplatforminsider/archive/2008/01/25/microsoft-sql-server-2008-roadmap-clarification.aspx

Tip: Find all The Rows Where Any Of The Columns Is Null Or Zero Or Both

This question is asked every now and then so I decided to do a little blog post. How can you quickly without writing a bunch of OR statements determince if any columns have a NULL value, a value of 0 or if the value is 0 or NULL.
To test for NULL is very easy, you just concatenate the columns since NULL + anything else is always NULL. Okay that also depends on a setting.

Run this

SET CONCAT_NULL_YIELDS_NULL ON
SELECT NULL + '1' --NULL

SET CONCAT_NULL_YIELDS_NULL OFF
SELECT NULL + '1' --1

As you can see if CONCAT_NULL_YIELDS_NULL is OFF then the result is 1

Now take a look at this


SET CONCAT_NULL_YIELDS_NULL ON
SELECT NULL + 1 --NULL



SET CONCAT_NULL_YIELDS_NULL OFF
SELECT NULL + 1 --NULL


So with numeric values it behaves differently. Either way by default CONCAT_NULL_YIELDS_NULL is set to on
To test for NULLS or zeroes you use NULLIF
To test for zeros you can combine COALESCE and NULLIF

Here is the code which shows all of that

CREATE TABLE #test(column1 int,column2 varchar(4),column3 float)

INSERT #test VALUES(2,'2',2)
INSERT #test VALUES(0,'1',0)
INSERT #test VALUES(null,'1',0)
INSERT #test VALUES(1,null,0)
INSERT #test VALUES(0,'1',null)
INSERT #test VALUES(null,null,null)



--Any column is Null
SELECT * FROM #test
WHERE column1 + column2+column3 is null

Output
------------
NULL 1 0.0
1 NULL 0.0
0 1 NULL
NULL NULL NULL



--Any column is Null or zero
SELECT * FROM #test
WHERE NULLIF(column1,0) + NULLIF(column2,0)+NULLIF(column3,0) is null

Output
-------------------
0 1 0.0
NULL 1 0.0
1 NULL 0.0
0 1 NULL
NULL NULL NULL




--Any column is zero
SELECT * FROM #test
WHERE NULLIF(COALESCE(column1,1),0) +
NULLIF(COALESCE(column2,1),0)+
NULLIF(COALESCE(column3,1),0) is null

Output
-------------------
0 1 0.0
NULL 1 0.0
1 NULL 0.0
0 1 NULL


DROP TABLE #test

Some Links To Blogs By Some Friends Of Mine

Since I have nothing useful to post today I decided to post some links to some of my friends

The first one is from someone in Belgium, his name is Christiaan Baes and he seems to like ORM tools like NHibernate. His blog is mostly about .NET. I'll forgive the fact that he is born 100 miles south by mistake.

The second one is from Mark Smith and he blogs about ASP.NET, SQL Server, HTML, CSS and other random thoughts. Mark's other site is http://aspnetlibrary.com/

The third one is from Denny Cherry, Denny has worked with shops running hundreds of SQL Servers with over half a billion transactions per second through out the farm.

The fourth one is from Alex Cuse and I don't think Alex himself knows what he is blogging about :-)

SQL Server 2005 Best Practices Analyzer (January 2008) Available For Download

This download is the January 2008 release of SQL Server 2005 Best Practices Analyzer.

Get it here: http://www.microsoft.com/downloads/details.aspx?FamilyId=DA0531E4-E94C-4991-82FA-F0E3FBD05E63&displaylang=en

The last two days have been the worst of my life

The last two days have been the worst of my life; it feels like he combination of a really bad hangover, the flu and a massive toothache. It all started on Wednesday afternoon; my tooth and the gum fell a little sore. Instead of going to the dentist like a normal person I decided to wait because it will go away. Thursday it fell worse and I had to ask for Motrin at work. I did not sleep at all Thursday night, I called my dentist at 6AM but he couldn’t see me until 12:20 PM. I figured he’ll give me a shot, clean out the tooth and I’ll be back at work at 2PM.
Well it turns out a root canal I had done 10 years ago acted up and they have to do a root end resection. My dentist doesn’t do root canals; he referred me to a specialist. The specialist is fully booked and doesn’t have an opening till Tuesday morning.
My dentist prescribed Oxycodone W/APAP (also known as Oxycontin or Roxicodone) and Amoxicillin. That stuff is pretty intense, your pain goes away but you are pretty much useless. The pain is gone but now my right cheek is swollen and I have to throw up every hour or so. I just hope all this ends by Tuesday, the fix the root canal and I can be at my desk by 12PM.
The reason I wrote this is that next time I say “I have no time to floss for five5 minutes I’ll do one minute instead” I can look back at this post and hopefully change my mind

Yet Another Date Teaser

It has been a while since my last teaser but here we go

What do you think the following returns?


SELECT CONVERT(datetime,'1/1/1') -CONVERT(datetime,1) + CONVERT(datetime,0)



How about this on SQL Server 2008


SELECT CONVERT(datetime2,'1/1/1'),CONVERT(datetime2,'01/01/01'),CONVERT(datetime2,'0001/01/01')


Now run this on SQL Server 2008

SELECT
ISDATE('1/1/1'),
ISDATE('01/01/01'),
ISDATE('001/01/01'),
ISDATE('0001/01/01')


Now just for fun run these 4 on SQL Server 2008, one of them will fail so run them one by one

SELECT CONVERT(datetime2,'1/1/1')
SELECT CONVERT(datetime2,'01/01/01')
SELECT CONVERT(datetime2,'001/01/01')
SELECT CONVERT(datetime2,'0001/01/01')

Compare the isdate output to the select statement, see the inconsistency?

Has Anyone Succeeded In Creating A Collision Between NEWID and NEWSEQUENTIALID

SQL Server 2005 introduced a new type of function to create a uniqueidentifier; the NEWSEQUENTIALID(). This new function has been created for performance reasons, each new value is greater than the previous value. In theory this means that the value will be inserted at the end of a page and not in the middle which can cause splits.

Let's run this code to see the difference

CREATE TABLE #TableSeqID (ColumnA uniqueidentifier DEFAULT NEWSEQUENTIALID(),
ColumnB uniqueidentifier DEFAULT NEWID())

INSERT #TableSeqID DEFAULT VALUES
INSERT #TableSeqID DEFAULT VALUES
INSERT #TableSeqID DEFAULT VALUES
INSERT #TableSeqID DEFAULT VALUES
INSERT #TableSeqID DEFAULT VALUES
GO


SELECT * FROM #TableSeqID

Output
-----------
BBF765FE-57BD-DC11-875F-000D5684F8D8 CE51B9E4-1640-47E2-87C6-6ADD46C63A87
BCF765FE-57BD-DC11-875F-000D5684F8D8 CA220BAB-462E-440E-829A-E0037CAF0D1F
BDF765FE-57BD-DC11-875F-000D5684F8D8 01748772-8155-4F83-A58F-CC3253DDD3F3
BEF765FE-57BD-DC11-875F-000D5684F8D8 9C4B2C87-AE33-4432-8310-3BE731179382
BFF765FE-57BD-DC11-875F-000D5684F8D8 1F84B827-F42A-4C47-8A1B-4B672B4402F1


As you can see ColumnB is random (Or at least pseudo-random) while ColumnA is not
Let's say you have a table with a billion rows, this table used NEWID() up till now. What will happen when you change the table to use NEWSEQUENTIALID(), could you get a duplicate?
I tried my best and filled up my 400GB External Seagate drive without success

Have you run into a collision, is it even possible?

I won't be flying on this sucker

FAA: Boeing's New 787 May Be Vulnerable to Hacker Attack

Boeing's new 787 Dreamliner passenger jet may have a serious security vulnerability in its onboard computer networks that could allow passengers to access the plane's control systems, according to the U.S. Federal Aviation Administration.

The computer network in the Dreamliner's passenger compartment, designed to give passengers in-flight internet access, is connected to the plane's control, navigation and communication systems, an FAA report reveals.

http://www.wired.com/politics/security/news/2008/01/dreamliner_security

The World Is Small, The Risk Of Your Data Being Stolen Is Not!

Remember the How Is Your Sensitive Data Encrypted In The Database? post I wrote a while back? A colleague just informed me that he got a letter from that same datacenter. The letter states that his personal data was on one of those servers which got stolen. I told him that this is the reason we encrypt our data and also why we encrypt outside of the DB. The world is small indeed.

Here is a pic of the letter

Use the *1 trick to do math with two varchars, this prevents the Invalid operator for data type. Operator equals subtract,type equals varchar message

Someone had code like this on the tek-tips forum

DECLARE @v varchar(24)
SELECT @v ='06029202400250029'

SELECT RIGHT(@v,4) -SUBSTRING(@v,10,4)

If you run this code, you will get the following message
Server: Msg 403, Level 16, State 1, Line 4
Invalid operator for data type. Operator equals subtract, type equals varchar.

Instead of casting to integers you can also use this little trick. You basically multiply one of the values by 1

DECLARE @v varchar(24)
SELECT @v ='06029202400250029'

SELECT RIGHT(@v,4) *1 -SUBSTRING(@v,10,4)



Another example. This doesn't work
SELECT '2' - '1'

This does work
SELECT '2' * 1 - '1'

Top Ten Posts Of 2007

Here is the list of the ten most popular posts for 2007 in terms of pageviews according to Google Analytics

1 The Sysinternals Troubleshooting Utilities have been rolled up into a single Suite of tools
2 Ten SQL Server Functions That You Hardly Use But Should
3 Become a better developer in 6 months
4 You Should Never Use IN In SQL To JOIN With Another Table
5 The Sad State Of Programmers Part 1 : The Phone Interview.
6 This has to be one of the worst planned projects in recent Database history
7 Login failed for user 'sa'. Reason: Not associated with a trusted SQL Server connection. SQL 2005
8 How Well Do You Interview And Do You Use Wizard Driven Programming?
9 Make Your Case Sensitive Searches 1000 Times Faster
10 The Sad State Of Programmers Part 2 : The In Person Interview

Top Ten Posts Of All Time

Here is the list of the ten most popular posts in terms of pageviews since I started collecting this info with google Analytics. I haven't updated this list since April or May

1 The Sysinternals Troubleshooting Utilities have been rolled up into a single Suite of tools
2 Ten SQL Server Functions That You Hardly Use But Should
3 Become a better developer in 6 months
4 SQL Query Optimizations
5 Login failed for user 'sa'. Reason: Not associated with a trusted SQL Server connection. SQL 2005
6 You Should Never Use IN In SQL To JOIN With Another Table
7 The Sad State Of Programmers Part 1 : The Phone Interview.
8 Five Ways To Return Values From Stored Procedures
9 This has to be one of the worst planned projects in recent Database history
10 How Well Do You Interview And Do You Use Wizard Driven Programming?

Updated 2008-01-02

Wow, talking about a rant against Ruby On Rails

Take a look at this post: Rails Is A Ghetto
This is probably one of the longest rants I have ever seen, interesting but be warned NSFW

You know What I Am Trying To Say :-)