1. Optimize SQL Server queries with these advanced tuning techniques | TechRepublic
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Optimize SQL Server queries
with these advanced tuning
techniques
By Tim Chapman
September 17, 2007, 11:57 AM PDT
Takeaway: The best way to tune performance is to try to write your queries in a number of
different ways and compare their reads and execution plans. Here are various techniques that you
can use to try to optimize your database queries.
Now that you know how to speed up your SQL Server database queries, you can start delving into
some of the more advanced tuning options. Google Docs For
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The best way to tune performance is to try to write your queries in a number of different ways and
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compare their reads and execution plans. Here are various techniques that you can use to try to
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optimize your database queries.
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If possible (and if it makes sense), I suggest using JOIN statements rather than subqueries to Free IPv6 Certification
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processing, which can slow down your queries.
Use explicit transactions
When data manipulation occurs in the database, the actions are written to the transaction log. If Keep Up with TechRepublic
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your statements are executing many DML statements, it might be a good idea to place them inside
of a transaction for performance purposes. Placing the statements inside of a transaction will
prevent all of the statements from being written to the transaction log serially. For example, the Your Email
following statement takes approximately seven seconds to execute on my laptop:
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CREATE InsertTable
(
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IDCol INT IDENTITY(1,1),
ColVal INT
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)
GO
DECLARE @Counter INT
SET @Counter = 1 Follow us however you choose!
WHILE @Counter 15000
BEGIN
INSERT INTO InsertTable(ColVal)
SELECT DATEPART(ms, GETDATE())
http://www.techrepublic.com/blog/datacenter/optimize-sql-server-queries-with-these-advanced-tuning-techniques/179[08/29/2012 3:06:42 PM]

2. Optimize SQL Server queries with these advanced tuning techniques | TechRepublic
SET @Counter = @Counter + 1
END
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If I wrap the INSERT statements inside of a transaction, it takes a little less than two seconds to
execute. This is because the statements are inside of a transaction rather than committed to a
transaction log until the transaction commits. This reduces the number of writes to the log.
DECLARE @Counter INT
SET @Counter = 1
BEGIN TRAN
WHILE @Counter 15000 PHOTO GALLERY (1 of 15)
BEGIN Curiosity's autonomous
INSERT INTO InsertTable(ColVal) 'seven minutes of...
SELECT DATEPART(ms, GETDATE())
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SET @Counter = @Counter + 1
END
COMMIT TRAN
Note: I advise you to use this approach with care. If there are too many statements inside a
transaction, it will increase the duration of the transaction, which increases the amount of time
locks are held on the objects inside of the transaction.
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When you use the UNION clause to concatenate the results from two or more SELECT More Videos »
statements, duplicate records are removed. This duplicate removal requires additional computing
to accomplish. If you are not concerned that your results may include duplicate records, use the
UNION ALL clause, which concatenates the full results from the SELECT statements.
Hot Questions View All
Use EXISTS when possible
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When you need to check for the presence of certain conditions, it is usually faster to use the
EXISTS function over COUNT(*). This is because COUNT(*) has to scan all records returned by
the statement, while EXISTS will return a true value as soon as it finds a record that meets the Switching from a Job to a career in
criteria.
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STATISTICS IO
There are different ways to determine the best way to write your queries. Two of my favorite 2 windows 7 won't shutdown and
methods are looking at the number of logical reads produced by the query and looking at graphical keeps switching on
execution plans provided by SQL Server Management Studio. For determining the number of
logical reads, you can turn the STATISTICS IO option ON. Consider this query: 2 can anyone suggest if any such
software exist with similar
SET STATISTICS IO ON
functionality?
SELECT * FROM SalesHistory
The following is returned in the Messages window in SQL Server Management Studio:
Ask a Question
Table 'SalesHistory'. Scan count 1, logical reads 33, physical reads 0, read-ahead reads 0, lob
logical reads 0, lob physical reads 0, lob read-ahead reads 0.
There are several bits of data returned by STATISTICS IO, but I am really only concerned with the Hot Discussions View All
logical reads portion because it will tell me the number of pages read from the data cache. This is
the most helpful to me because it will stay constant when I run the same query, which is important
221 Should developers be sued for
because there are sometimes external factors that might vary the execution time of my queries,
security holes?
such as locking by other queries.
When I’m tuning my queries, my goal is to get the number of logical reads as low as possible. 79 The sitting duck that is open
Fewer logical reads typically leads to faster execution times. source
Fine tuning 27 Five fast Windows desktop search
utilities
In a future article, I will look at how you can use the graphical execution plans created by SQL
Server to fine tune your queries.
24 Five speedy Windows desktop
Tim Chapman is a SQL Server database administrator and consultant who works for a bank in search apps
Louisville, KY. Tim has more than eight years of IT experience, and he is a Microsoft certified
Database Developer and Administrator. If you would like to contact Tim, please e-mail him at
Start a Discussion
chapman.tim@gmail.com.
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3. Optimize SQL Server queries with these advanced tuning techniques | TechRepublic
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Comments Follow via:
Staff Picks Top Rated Most Recent My Contacts See All Comments
how to connect vb.net form to databace sqlserver. 0
mekashifraza 16th Jul 2009 Votes
i have written all the required codes like connection ,data adapoter,dataset.but it not
working
View in thread
Never ending update 0
JBNY Updated - 21st Oct 2007 Votes
I ran this query in the Query Analyzer for 6 hours and then gave up. 29 million recs at
24GB. Update A Set Acctid = B.Acctid From B Where Substring(VendId,5,4) =
B.VendId4 I did a link from Access and... Read Whole Comment +
View in thread
Damn right it's odd 0
Tony Hopkinson 20th Sep 2007 Votes
One column look up by primary key closed set of integers 1 - 1000 ? The colleague
was testing large batch queries in a payroll engine, I figured there were a lot of ways
that might go different, so I... Read Whole Comment +
View in thread
See all comments
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4. Optimize SQL Server queries with these advanced tuning techniques | TechRepublic
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http://www.techrepublic.com/blog/datacenter/optimize-sql-server-queries-with-these-advanced-tuning-techniques/179[08/29/2012 3:06:42 PM]