September 2009 - Posts
SQLBits is not around to make moeny, its here to build
the SQL Community. What that means is that when start to cover our costs then
there is no point in charging people more. We've reached that point and so what
we've done is push back the end of the early bird to the end of October.
This means that if you need a little longer to convince your bos you should
go to the best SQL Server conference around then you now have 4 more weeks.
I look forward to seeing you all there and hope you can convince your boss
its well worth your while. It must be the best value training you can get for
SQL Server.
Oh and if you can't get your Boss to open his wallet then don't forget it's
still free to come on the Saturday.
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If you are umming and ahhing about registering for
SQLBits. Get in quick as the early bird ends on Wednesday.
If you are going to the Data Management Conference today then I will see you
there and if you are lucky ther migth be some interesting giveaways with regards
to SQLBits. So come and see us, I think a group of us will be in an "Ask the
experts" type area.
Oh and don't forget to get your pictures for the SQLBits mugshot competition.
We will be deciding on the winner at our committee meeting tonight (Tuesday).
There have been some great entries so far.
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This error occurs when you try and populate a table using
the OUTPUT clause AND the target of the main statement has a trigger on it.
Shame, currently I don't know of any work around. BOL clearly states that you
can't have triggers and populate an table from the OUTPUT
clause.
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Just a gentle reminder that if you are considering
coming to SQLBits then you need to register and pay by next Wednesday in order
to get the £100 early bird discount.
Don't forget that if you book 6 places on the full conference then you get a
20% discount.
The numbers are looking good so it will be another great
SQLBits.
Also don't forget the Mug Shot competition for a chance to win a free ticket
and accomodation for the whol conference. The entries are building up, but there
is still a great chance to win.
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If you've been considering going to SQLBits and looked
at hotel prices for the Celtic Manor. You might have found the Thursday or
Friday night cheaper using laterooms etc. The Hotel have kindly agreed to match
the price on these sites as long as they have allocation left. Whats more if
you've already booked and said you are coming to SQLBits then your room price
should have been reduced.
So now you can get a superior double inc breakfast on Thursday and
Friday for only £99.
There should be quite a few of us staying in the Hotel so I look forward to
seeing you there.
This price will only be available whilst they have allocation so get in
quick.
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The following are the questions asked
following the query tuning webcast I did with Kevin Kline
If you have any further questions
please let me know.
Hue Holleran
Asked:
Shouldn't the _primary_ objective be to minimise _overall_ server load, ie.
reducing logical reads is the most important thing from stats io (followed by
CPU from stats time) ?
Simon Sabin
Answered :
Yes you are correct CPU is also important and SET STATISTICS TIME can provide
that. Also sys.dm_exec_requests can also provide the CPU used per
request
Neesha Kanji
Asked:
Could you also save a subquery result set in a temp table and join that on the
main query? Would the query be just as quick?
Simon Sabin
Answered: Sometimes, however including the join in the query gives the optimiser the
option to flatten the query and possibly save reading data multiple times. Often
writing as a derived table can be a better solution. Using the temp table can
often aid developing the code as its easier to test each section. BUT that
doesn't mean you should split up all your queries as that removes the benefits
of doing SET based processing.
Phil Pinto
Asked: Recommend a performance book,
please
Simon Sabin
Answered: Personally you need to understand the internals to be able to understand
performance. And so the Internals books are good. I learnt using a book from Ken
Henderson many years ago so its worth trying his book
http://www.amazon.com/Gurus-Guide-Server-Architecture-Internals/dp/0201700476/ref=sr_1_4?ie=UTF8&s=books&qid=1253631035&sr=1-4
Kevin Kline
(Qsft) Answered: I also like Kalen Delaney's internals book. If I could only own one SQL
Server book, it'd be hers. Itzik Ben-Gan's T-SQL books are also
excellent.
Phil Pinto
Asked:
Thanks for book recommended. Indexes are useful but can be a maintenance
overhead if only a very infrequent used query.
Kevin Kline
(Qsft) Answered: KK> I also like Kalen Delaney's internal book - in fact, if I could only
own one book, Inside SQL Server would be the one.
*** B
aker Asked: database query in SSMS (previously QA) allows
one do obtain ESTIMATED Query Plan (i.e. Ctrl-L). The question is does the
ACTUAL QP always follow that "compile-time" decision strategy, or may it deviate
(eg the SET STATISTICS IO ON which is actual after the statement completion)?
For example the DEC RdB database (now subsumed into Oracle) would dynamically
review several strategies : perhaps pick a simple FAST-FORWARD approach, but
might switch to a more complex strategy after some pause (ie jettison the FF
workinprogress)
Simon Sabin
Answered: The only different between compile and execution time is the parallelism.
The engine might decide to remove parallelism and run a non parallel
query
Richard
Asked: 2008 SSMS suggests missing indexes
in Query Plans, regardless of version it is looking at
Simon Sabin
Answered: Very good point. Its also worth noting that just because a missing index
warning doesn't come up doesn't mean that there isn't a better index option
available
Andy Irving
Asked: it's only automatic use of indexed
views which is EE only, in standard you have to use NOEXPAND
hint
Simon Sabin
Answered: Very true, often even in EE you need to use NOEXPAND because the indexed
view isn't considered until late on in the query optimisation phase
*** Baker
Asked:
please highlight diff between temp
table and temp table variable. can you index a table variable? what about PK
(implied CI) perhaps #temp better than @temp for certain cases ?
thanks!
Simon Sabin
Answered: temp table and table variables use the same structure and are stored in
tempdb. Table variables are not in memory structures. Depending on the load of
the server either may be held in memory and both are stored on disk. Temp tables
don’t have statistics which means that if you join to them you can result in
poor query plans. Temp tables do have statistics but that itself can cause
problems as it can cause recompilations of your code. You are correct that you
cannot create indexes on a table variable, however you can indirectly create
them by creating primary key and unique constraints. You can create indexes on
temp tables. I generally say that table variables are great for small rows or
where you are only going to be scanning from the table variable.
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If you are registered on the site you can now vote on the
sessions you want to see at the next SQLBits.
Click here to make your vote
ts vital that you vote so that you get the sessions. If you don't we've no
idea it you would prefer index tuning or piano tuning.
So please spend some time looking for the sessions you really want to see. If
you are coming on Friday and Saturday its even more important you vote as we
have some scope to repeat sessions if they are very popular.
So get voting
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Dear SQL Server
Widow,
As a partner of a SQL
Server Professional, I am sure you may be aware of the quirkily named
SQLBits conferences organized in various parts of the country twice each year.
Your partner may have disappeared for a weekend and returned enthused and eager
to try out the many new things he has learnt, all SQL Server related
unfortunately. Up to now this may have been a bit of a chore having to put up
with them going on about this, but now that doesn’t have to be the
case.
The next SQLBits
conference, cunningly called “SQLBits goes West” will be at the luxury Golf and
Spa resort, the Celtic Manor. Perfect for a relaxing weekend
away.
If your partner books
before the 30th September they will save up to £200 on the registration fee.
That’s £200 that you could use on one of the Spa
Experience days provided by the resort. You could just choose
your own combination from the range of therapies, massages, holistic treatments
on offer; including the Rasul Mud Ritual, Dry Floatation and Hydrotherapy,
Facials, Manicures and Pedicures.
So make sure they signs
up at www.sqlbits.com so you can get treated to the relaxing
weekend you are entitled to at one of the top Health Spas in the
UK.
Yours
faithfully,
SQLBits Committee
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If you want a free trip to SQLBits then you;ve got 1
extra week to submit entries. We've only got 5 entries so far and so the chance
of winning is very high.
To have a look at the current entries and submit your
pictures go to the Mugshot
competition page
So far we've got a mug on holiday
and one in a field of cows
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Welcome to two new SQL Bloggers Steve Simon
http://sqlblogcasts.com/blogs/stevesimonsays/default.aspx and Dave Ballantyne http://sqlblogcasts.com/blogs/sqlandthelike/default.aspx
If you want to start blogging them let me know. Either email me if you have
my email addres or use the contact form http://sqlblogcasts.com/blogs/simons/contact.aspx
Happy blogging.
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