/* */ SQL Works: October 2012

Monday, October 22, 2012

SQL Server Wait_Type full description table

In preparing for another post to continue identifying blocking within your database, I found I did not have a full description for each wait_type, so I took the data from MSDN and created a table that holds all the full descriptions of each wait type, original data here. This was taken from SQL Server 2012 material, your mileage may vary in other versions.

Here is the table I used, very simple:

CREATE TABLE dbo.Wait_Type_Description
Wait_type VARCHAR(50) NOT NULL,
Wait_Type_desc VARCHAR(8000) NOT NULL

and I am joining it like this, again super simple example:

FROM sys.dm_exec_requests der
JOIN dbo.wait_Type_description wtd
ON der.wait_type wtd.wait_type

All 345 INSERT statements can be found here, sorry this is obnoxious to look at you may download the script or cut and paste it below.

Thursday, October 18, 2012

Are your customers abusing you?

Do you have Customers that you dread talking to? You know the types, they are not happy, ever, and have a seemingly endless stream of new requirements (read as: demands) of you and your team. While this post is geared toward those of us who have or are currently working in a large enterprise where database teams and IT specifically work 'for' other internal teams, it applies to everyone with customers or users.
In a large company, you often don't get to 'charge' for your services, the end users get to create requirements and hand them to you, and you don't get to make any requests of them in response, in essence your services are "free". Whenever you offer something for free, you are going to get a somewhat irrational response, people are really effected by the word or concept of "free". Dan Ariely writes about this concept in his book "Predictably Irrational", he shows us through experimentation that when the price is free, the demand will increase incredibly fast, and at the expense of reasonable decision making. I think this holds true in most transactions, whether its free cell phones or free software, if it's free demand will increase beyond what could be expected from otherwise rational consumers. to quote Dan Ariely (@danariely):
... First of all, let me say that there are many times when getting FREE! items can make perfect sense. If you find a bin of FREE! athletic socks at a department store, for instance, there is no downside to grabbing all the socks you can. The critical issue arises when FREE! becomes a struggle between a free item and another item - a struggle in which the presence of FREE! leads us to make a bad decision. *
I have never seen this concept more ably demonstrated than I have working in a large corporate IT department. There are other examples, for example this post on SQLServerCentral's forums is a great example of exactly the same thing happening but in a smaller company
Amazing what a little regulation does for requirements! After looking into PCI requirements, I also found that CSC (or other authentication methods) can never be stored. So when I brought this to the attention of the department head and suggested we look into our options with the lawyer, he quickly rescinded that particular requirement. Turns out, the CSC is not required by our CC processing software, that requirement was just put there "just in case we ever needed it."  (full thread here)
 This is a great example, since there was no cost involved, an unnecessary and in this case legally precarious, requirement was thrown in 'just in case'. For those suffering under the pile of "nice to haves" and "just in case" requirements and constant revisions, what can be done? I have found that even implementing a nominal cost for IT services can have a big impact on the way your customers will view your services. When it comes to nominal cost, it does not have to be monetary, it can be additional regulatory overheard, legal or financial risk, or an unacceptable increase in time lines that brings the needed 'costs' into the equation. The example from the recent forum thread above did not involve any financial costs, the cost was in the potential legal exposure, and the cost was too great. So how does one go about implementing a cost structure in a corporate environment that realistically does not allow you to actually charge money for your interdepartmental services?
If there is a cost center or ledger you can charge, even a nominal amount, then do it. Having to reconcile charges made between departments really isn't money being 'spent' by the company, however having to justify the expense is usually costly enough in terms of hours and headaches to really give someone pause as to whether the expenditure is necessary. I have seen this implemented and work with surprising effectiveness, if the only rationale for requesting something is "why not", then all you need to do is supply that reason. If the concept of charging for a service won't work in your workplace, then charge your customers in a different way, with time. If a requirement is changed or added last minute, address it with the requester by showing him/her what else you are working on and what will suffer delays because of this change, your charging them the opportunity cost of this new item. By having to look over everything they are asking of you and weigh the new requirement against the others, value judgments will be made and unimportant items eliminated quickly.

If you are dealing with a customer or client that is not internal, but are actual customers in the true sense of the word, then it can be trickier to handle. as evidenced here on TechCrunch in a post by @JasonKincaid
there can be a large cost to FREE! promotions, including the overhead to support additional users both with bandwidth/hardware/storage type needs, as well as the user support requirements of exponentially growing a user base that needs support but has paid you nothing in return .In this case there may be a simple answer, stop giving your app away free and you wont have these problems, but if these freeloaders are also paying customers of another of your products or services, alienating them could be costly. You will need or determine whether the traffic and 'exposure' your brand or product is getting has any payoff down the road.

So when you are considering your next set of requirements or thinking of offering a service or product for free, ask your potential customers or users, what is this worth to you? If they can't say, be prepared to propose a value yourself and be confident in asking for compensation for your hard work, and both you and your consumer will be satisfied that value is being exchanged for value.

*Ariely, Dan Predictably Irrational. New York: Harper Perennial 2010
Predictably Irrational, Revised and Expanded Edition: The Hidden Forces That Shape Our Decisions

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Wednesday, October 17, 2012

Deadlock and blocking in SQL Server - Part 2

With SQL Server 2005 a set of dynamic management views were introduced to allow you better visibility into what exactly was happening within the instances of SQL Server you manage or use. The below script takes the outdated sys.sysprocesses and fn_get_sql functions (which still work but are deprecated) and replaces them with new DMVs sys.dm_exec_requests and sys.dm_exec_sql_text.
Additionally it more narrowly defines the SQL statement being executed by both the blockee and blocker by trimming down the full text of the script or procedure and only returning the actual code currently executing. This is done by using the statement_start and statement_end offset values in the sys.dm_exec_requests view.
There is a lot more information available on what currently executing statements are doing within your instance, but this script will get you some of the most important information about who is blocking who quickly. I will expand on this again in the near future with more details about what resources are being contested, and other metrics.

   Created: October 2012
   Author: SQLWorks blog
   URL: http://www.SQLWorks.blogspot.com
   10/17/2012 - replaced sysprocesses with new DMV sys.dm_exec_requests
              - replaced fn_get_sql with new DMV dm_exec_sql_text
              - Used SUBSTRING and statement_offet values to determine exact statement that               is currently executing
              - instead of returning entire command or proceure

DECLARE @sql_handle TABLE(blockee_spid INTblockee_cmd VARCHAR(MAX), blocker_spid INTblocker_cmd VARCHAR(MAX))
INSERT INTO @sql_handle
SELECT sp1.session_id AS blockee_spid,

CASE WHEN sp1.statement_start_offset >= THEN sp1.statement_start_offset
CASE WHEN (sp1.statement_end_offset-sp1.statement_start_offset) >= THEN                      (SELECT LEN(TEXTFROM sys.dm_exec_sql_text(sp1.sql_handle))
ELSE (sp1.statement_end_offset-sp1.statement_start_offsetEND),

sp1.blocking_session_id AS blocker_spid,

CASE WHEN sp2.statement_start_offset >= THEN sp2.statement_start_offset
CASE WHEN (sp2.statement_end_offset-sp2.statement_start_offset)<= THEN          (SELECT LEN(TEXTFROM sys.dm_exec_sql_text(sp2.sql_handle))
ELSE (sp2.statement_end_offset-sp2.statement_start_offsetENDAS blocker_cmd

FROM sys.dm_exec_requests sp1
JOIN sys.dm_exec_requests sp2
ON sp1.blocking_session_id sp2.session_id
CROSS APPLY sys.dm_exec_sql_text((sp1.sql_handle)) AS blockee_cmd
CROSS APPLY sys.dm_exec_sql_text((sp2.sql_handle)) AS blocker_cmd
WHERE sp1.blocking_session_id <> 0

*FROM @sql_handle

Using the same test data from Part 1 of this post, I added a second simple SELECT query that would be blocked by the update loop and then ran the above statement. The results show the way that the statements are blocked by each other.

Blocking script results multiple spid blocked TSQL SQL Server

What you can see here is that spid 52 (the update loop) is blocking spid 56 (the first SELECT) and then spid 56 is blocking spid 53 (the second SELECT). These results are a bit hard to look at, so in the next post I will modify how they are displayed and get a more usable result set returned.

Go back to Part 1 - blocking and deadlocks

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Tuesday, October 16, 2012

Deadlocks and blocking in SQL Server

As a DBA you are probably faced with the issue of users blocking each other's queries in your databases and potentially deadlocks between queries as well. Here is how I identify and resolve those issues. This method is simple and quick and probably all you need for most situations, there are much more elaborate ways of tracing and troubleshooting these, but for user queries and in-the-moment identification of issues, this way almost always works.

First, the difference between blocking or contention and a deadlock in simple terms, blocking is when one spid or query blocks another from using a resource or placing the lock it needs on said resource, and a deadlock is when two users or queries each holds a resource the other needs next and neither will let go, so the engine chooses a 'victim' and ends the standoff by killing one query. Again this is really simplified but its all you need to know to get started. Now how do we identify when each scenario is happening?

Lets set up some test data first:

/* Created: October 2012
   Author: SQLWorks Consulting blog
   URL: http://www.SQLWorks.blogspot.com

CREATE TABLE [dbo].[EmployeePerf](
[EmployeeID] [int] NOT NULL,
[EmployeeName] [varchar](25) NOT NULL,
[Sales] [int] NULL,
[TimePeriod] [int] NULL

-- test data
INSERT INTO dbo.EmployeePerf VALUES(1,'Tony',100,'1')
INSERT INTO dbo.EmployeePerf VALUES(1,'Tony',300,'2')
INSERT INTO dbo.EmployeePerf VALUES(1,'Tony',200,'3')
INSERT INTO dbo.EmployeePerf VALUES(1,'Tony',150,'4')  

This is just a table I had set up already on my server to test something else, so I am reusing it, the contents of the table are not really relevant to the discussion on database contention.

So now we need two queries, one to block the other for our testing:
-- Looping update to create a lock for demonstration
DECLARE @sales INT = 100
@sales 500000
SET sales @sales
WHERE Employeename 'tony' AND timeperiod 1

SET @sales @sales +1


and in a second window, you will run this concurrently and it will be blocked by the first:

-- select statement that will be blocked by above update statement for demonstration
-- Run this in a different query window!

FROM dbo.EmployeePerf

So now that we have blocking occurring, what do we do about it? Well first I always like to know who is blocking who, and the commands being attempted by each party. To find that out there are several methods, here is the one I use in SQL Server 2012:

DECLARE @sql_handle TABLE(blockee_spid INTblockee_cmd VARCHAR(MAX), blocker_spid INTblocker_cmd VARCHAR(MAX))INSERT INTO @sql_handle
SELECT sp1.spid AS blockee_spidblockee_cmd.TEXT AS blockee_cmdsp1.blocked AS blocker_spidblocker_cmd.TEXT AS blocker_cmd
       FROM sys.sysprocesses sp1
           JOIN sys.sysprocesses sp2
           ON sp1.blocked sp2.spid
       CROSS APPLY sys.dm_exec_sql_text((sp1.sql_handle)) AS blockee_cmd --updated
       CROSS APPLY sys.dm_exec_sql_text((sp2.sql_handle)) AS blocker_cmd --updated
       WHERE sp1.blocked <> 0

SELECT *FROM @sql_handle

This uses the sys.sysprocesses system view to see what is blocking and being blocked and then calls the fn_get_sql function for each to determine what code is being run. If you run the two queries above, then run this script in a third window you will get the below results:

As you can see, it provides the spid of the blocker and blockee, as well as the commands being run by each. There is so much more to delve into on this subject but this will get you moving, and give you a quick way to answer the recurring user question we all love "Who is blocking my query?!?!"

-- EDIT - updated with suggestions from @AaronBertrand of SQLBlog.com
-- changed fn_get_sql to sys.dm_exec_sql_text

-- EDIT - changed formatting of code so comment lines didn't run over code
  -- EDIT - again fixed weird formatting in the code snippets

coming tomorrow, Part 2 - new version using dm views

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SQL code format for web pages

Just found this piece of genius: http://extras.sqlservercentral.com/prettifier/prettifier.aspx 

Paste your code and it will format it to appear like it does in SSMS, and supply you with the HTML. I know there are many, many sites that offer this, but this one actually gets it right according to SSMS colorization. Thank you SQL Server Central.

Monday, October 15, 2012

Logitech K810 - one keyboard for phone, tablet and computer

I love this idea, but more for the fact that I could pair both my laptops to this one keyboard and switch between them without having to plug/unplug anything. It's a keyboard that can be paired with up to three devices, including computers, tablets and phones, and hot swapped between them.

Logitech K810 write up from geekbeat.com

They are not out yet, full details from Logitech here:
Logitech Product page
But preorders are available for $99 USD, no number pad, but I might still sign up

Friday, October 12, 2012

You probably need a new keyboard

Need a new keyboard? So did I, so I checked a few out, went to Best Buy and opened a lot of boxes to test the keys, went to Staples and did the same, then shopped around Newegg, TigerDirect and Amazon looking for the best prices of course, and I ended up with an HP Elite Wireless V2 keyboard (ended up getting it at Best Buy). I may have some bias here because I have an HP Elite book that I like a lot, but this is one of the best keyboards I have ever used. It is very thin, but very rigid and strong, the keys are easy to use and feel great over long periods of use (8+ hours a day). If you haven't gotten a new keyboard lately, do yourself a favor and get a better one, if you are a professional and spend 8 or more (sometimes many more) hours in front of the keyboard every day you owe it to yourself to get a decent one. The link in this image is the best price I could find.

The Elite V2 is also very thin and light, you could bring it with you on a plane if you had to and you really wouldn't be giving up much space in your carry on. Overall this seems to be the best value in this price range, you can spend a hell of a lot more if you really wanted to (see example below) but for someone who is just looking for a tool to do their work, this is the way to go in my opinion.

For those who have more money than sense, please click here:

Optimus maximus keyboard Art Lebedev

How is the role of the 'Analyst' changing in a data driven world?

     I remember the days when I was considered a top notch resource when it came to answering data driven questions. My Excel sheets were sparkling, my PowerPoint slides were beautiful, and my MS Access database was driving it all. In those days, when you needed to know how many widgets the sales team had sold, you asked them for their results sheet, and probably received it by email. When you needed to see attendance records for the call centers, they replied with their own spreadsheet, and a few paper based updates perhaps. After you had all your data collected and entered or imported to Access you could do with it what you pleased, and get some results worth sharing. But those days are gone, over the last 10 years I have witnessed an amazing transition from the scenario I describe above to the new paradigm of the 'Analyst' as power user and SQL dabbler. The data companies house internally is larger and more broad than ever before and growing quickly, and in order to present informed conclusions about a business, market or customer group, you need to be able to intelligently ask questions of these large stores of data.
     Enter the new 'Analyst', someone who is expected to know how to interact with databases like never before and to collate and present data from varied sources. Where a job description from those bygone days might have read "requires advanced MS Office suite knowledge" it is typical now to see requirements similar to "Must be familiar with SQL querying and tools such as SQL Server, Toad for SQL or PC SAS in order to gather results".

Wednesday, October 10, 2012

Searching Across SQL Server Part 3

To give other users access to use your SQL search script, but keep it centrally managed and compiled on your server, you need to implement it as a stored procedure or function. The choice between stored procedure and function for most installations is largely personal preference, I chose to go with a stored procedure, if you're interested in the relative merits of each there is some good reading here:

I have placed the code for the full stored procedure on git hub here: GitHub Full Procedure Code
I will only display the changes I made in the interest of keeping this post from filling your screen with code.
Created by SQLWorks blog 2012

CREATE PROCEDURE Usp_search @search_str VARCHAR(1000)
    SET nocount ON 


I added the CREATE statements in the beginning, and made a couple of tweaks to the dynamic SQL in order to prevent duplicate results, see comments in the full code for details.

The usage is different of course, now you will use EXECUTE to run your new procedure and pass in the string you are searching for as a parameter as shown below.

EXECUTE Usp_search 'Employees' 

Which yields the following results showing this keyword is present in two object names:
SQL Search procedure table results

Let's pass in a keyword present in column names:

EXECUTE Usp_search 'EmployeeID' 

The results yielded are shown below:
SQLSearch procedure column results

Now you can incorporate this procedure into jobs or other processes on your database server or in your applications, or base a report on it to allow users to search for items in your databases as well.

Part 4 coming up next, creating an SSRS report around this procedure

Go back to Part 1
Go back to Part 2

Tuesday, October 9, 2012

NTILE ranking functions in SQL Server

Following the previous post on the ROW_NUMBER function, lets look at other rank type functions in SQL Server and how you can use them.
Books Online does a good job of explaining the syntax, so I will link to it here and not go into too much detail beside to place this link. Ranking functions via MSDN

So, now that you have the syntax, where would you use these functions? what kind of questions can they help you answer with your data? Here is a scenario, suppose your boss asks you to apply the 10-80-10 rule (placing employees into performance groups comprising 10% (high) 80% (medium) 10% (low) ) to a group of employees every week, so they can evaluate who is performing above and below expectations. You could use any of the ranking functions to achieve this, but the quartile function works the best because it will always divide the group of employees into the number of quartiles you specify, so if people come and go you wont have to worry about counting how many are in each rank to determine over all percentile. Example below.

Here is the test data first:

CREATE TABLE dbo.EmployeePerf
employeeid INT NOT NULL,
employeename VARCHAR(25) NOT NULL,
sales INT,
timeperiod INT

INSERT INTO employeeperf VALUES (1, 'Tony', 100, 1)
INSERT INTO employeeperf VALUES (1, 'Tony', 300, 2)
INSERT INTO employeeperf VALUES (1, 'Tony', 200, 3)
INSERT INTO employeeperf VALUES (1, 'Tony', 150, 4)
INSERT INTO employeeperf VALUES (1, 'Meg', 900, 1)
INSERT INTO employeeperf VALUES (1, 'Meg', 400, 2)
INSERT INTO employeeperf VALUES (1, 'Meg', 500, 3)
INSERT INTO employeeperf VALUES (1, 'Meg', 850, 4)
INSERT INTO employeeperf VALUES (1, 'Ben', 100, 1)
INSERT INTO employeeperf VALUES (1, 'Ben', 40, 2)
INSERT INTO employeeperf VALUES (1, 'Ben', 50, 3)
INSERT INTO employeeperf VALUES (1, 'Ben', 90, 4)
INSERT INTO employeeperf VALUES (1, 'Jim', 1000, 1)
INSERT INTO employeeperf VALUES (1, 'Jim', 3000, 2)
INSERT INTO employeeperf VALUES (1, 'Jim', 2000, 3)
INSERT INTO employeeperf VALUES (1, 'Jim', 1500, 4)
INSERT INTO employeeperf VALUES (1, 'Abigail', 90, 1)
INSERT INTO employeeperf VALUES (1, 'Abigail', 40, 2)
INSERT INTO employeeperf VALUES (1, 'Abigail', 500, 3)
INSERT INTO employeeperf VALUES (1, 'Abigail', 80, 4)
INSERT INTO employeeperf VALUES (1, 'Mike', 1000, 1)
INSERT INTO employeeperf VALUES (1, 'Mike', 840, 2)
INSERT INTO employeeperf VALUES (1, 'Mike', 350, 3)
INSERT INTO employeeperf VALUES (1, 'Mike', 190, 4)
INSERT INTO employeeperf VALUES (1, 'John', 10, 1)
INSERT INTO employeeperf VALUES (1, 'John', 30, 2)
INSERT INTO employeeperf VALUES (1, 'John', 20, 3)
INSERT INTO employeeperf VALUES (1, 'John', 10, 4)
INSERT INTO employeeperf VALUES (1, 'Deb', 500, 1)
INSERT INTO employeeperf VALUES (1, 'Deb', 400, 2)
INSERT INTO employeeperf VALUES (1, 'Deb', 200, 3)
INSERT INTO employeeperf VALUES (1, 'Deb', 180, 4)
INSERT INTO employeeperf VALUES (1, 'Peter', 100, 1)
INSERT INTO employeeperf VALUES (1, 'Peter', 740, 2)
INSERT INTO employeeperf VALUES (1, 'Peter', 650, 3)
INSERT INTO employeeperf VALUES (1, 'Peter', 890, 4)
INSERT INTO employeeperf VALUES (1, 'Bill', 230, 1)
INSERT INTO employeeperf VALUES (1, 'Bill', 450, 2)
INSERT INTO employeeperf VALUES (1, 'Bill', 245, 3)
INSERT INTO employeeperf VALUES (1, 'Bill', 180, 4)
INSERT INTO employeeperf VALUES (1, 'Julie', 50, 1)
INSERT INTO employeeperf VALUES (1, 'Julie', 40, 2)
INSERT INTO employeeperf VALUES (1, 'Julie', 20, 3)
INSERT INTO employeeperf VALUES (1, 'Julie', 10, 4)
INSERT INTO employeeperf VALUES (1, 'Paul', 1000, 1)
INSERT INTO employeeperf VALUES (1, 'Paul', 700, 2)
INSERT INTO employeeperf VALUES (1, 'Paul', 600, 3)
INSERT INTO employeeperf VALUES (1, 'Paul', 590, 4)

Now to divide these employees up into the requested 10-80-10 we can apply the NTILE() function like this:

SELECT employeeid, employeename, sales, timeperiod, Ntile(10) OVER (ORDER BY sales) AS Quartile
  FROM employeeperf 
  WHERE timeperiod = 1

This gives us our results, the employees group in 10% increments by sales for the time period we care about, but what if you don't want to re-run it for each time period, and you only want to display those in the top and bottom 10% brackets? A common need for performance management, lets change the code to the following:

;WITH salescte 
SELECT employeeid, employeename, sales, timeperiod, 
     Ntile(10) OVER (partition BY timeperiod ORDER BY sales) AS Quartile  -- added PARTITION BY
  FROM employeeperf 
  --WHERE TimePeriod = 1    <-- removed to include all periods 

SELECT employeeid, employeename, sales, timeperiod, quartile 
  FROM salescte 
  WHERE quartile IN (1, 10) 
    ORDER BY timeperiod, quartile ASC

And the results are exactly what we wanted, the top and bottom 10%

NTILE ranking function results
My random test data is a bit skewed, as you can see some sales are radically different, if you were in a more normalized environment the number of people in each quartile would be more even. Hope this is useful.