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  • Always use dtexec.exe to test performance of your dataflows. No exceptions.

    - by jamiet
    Earlier this evening I posted a blog post entitled Investigation: Can different combinations of components effect Dataflow performance? where I compared the performance of three different dataflows all working to the same overall goal. I wanted to make one last point related to the results but I thought it warranted a blog post all of its own. Here is a screenshot of one of the dataflows that I was testing: Pretty complicated I’m sure you’ll agree. Now, when I executed this dataflow in the test it was executing in ~19seconds however in that case I was executing using the command-line tool dtexec. I also tried executing inside the BIDS development environment and in that case it took much longer – 139seconds. That’s more than seven times as long. The point I want to make is very simple. If you are testing your dataflows for performance please use dtexec. Nothing else will suffice. @Jamiet

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  • SQL Saturday Birmingham #328 Database Design Precon In One Week

    - by drsql
    On September 22, I will be doing my "How to Design a Relational Database" pre-conference session in Birmingham, Alabama. You can see the abstract here if you are interested, and you can sign up there too, naturally. At just $100, which includes a free ebook copy of my database design book, it is a great bargain and I totally promise it will be a little over 7 hours of talking about and designing databases, which will certainly be better than what you do on a normal work day, even a Friday....(read more)

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  • Does multiple files in SQL Server when using RAID help reduce conflicts in growth and file-locking?

    - by Dr Giles M
    I've been reading around and get the impression that if you are using RAID then using multiple SQL Server files within a filegroup won't yeild any more improvements, and the benefits are purely administrative (if you started to run out of space or wanted to partition off data into managable chunks for backups/balancing the data around your big server room). However, being a reasonably savvy software person, it's not unthinkable to hypothesise that, even for smaller databases that SQL Server will perform growth and locking operations (for writes) on a LOGICAL file basis, so even if you are using RAID, it seems to make sense to have multiple files in a file group to balance I/O, or does the time taken to reconstruct the data from distributed filegroups outweigh the benefits of reduced locking? I'm also aware that the behaviour and benefits may be different for tables/indeces/log. Is there a good site that distinguishes the benefits of multiple files when RAID is already in place?

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  • Should we have a database independent SQL like query language in Django?

    - by Yugal Jindle
    Note : I know we have Django ORM already that keeps things database independent and converts to the database specific SQL queries. Once things starts getting complicated it is preferred to write raw SQL queries for better efficiency. When you write raw sql queries your code gets trapped with the database you are using. I also understand its important to use the full power of your database that can-not be achieved with the django orm alone. My Question : Until I use any database specific feature, why should one be trapped with the database. For instance : We have a query with multiple joins and we decided to write a raw sql query. Now, that makes my website postgres specific. Even when I have not used any postgres specific feature. I feel there should be some fake sql language which can translate to any database's sql query. Even Django's ORM can be built over it. So, that if you go out of ORM but not database specific - you can still remain database independent. I asked the same question to Jacob Kaplan Moss (In person) : He advised me to stay with the database that I like and endure its whole power, to which I agree. But my point was not that we should be database independent. My point is we should be database independent until we use a database specific feature. Please explain, why should be there a fake sql layer over the actual sql ?

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  • Smart defaults [SSDT]

    - by jamiet
    I’ve just discovered a new, somewhat hidden, feature in SSDT that I didn’t know about and figured it would be worth highlighting here because I’ll bet not many others know it either; the feature is called Smart Defaults. It gets around the problem of adding a NOT NULLable column to an existing table that has got data in it – previous to SSDT you would need to define a DEFAULT constraint however it does feel rather cumbersome to create an object purely for the purpose of pushing through a deployment – that’s the situation that Smart Defaults is meant to alleviate. The Smart Defaults option exists in the advanced section of a Publish Profile file: The description of the setting is “Automatically provides a default value when updating a table that contains data with a column that does not allow null values”, in other words checking that option will cause SSDT to insert an arbitrary default value into your newly created NON NULLable column. In case you’re wondering how it does it, here’s how: SSDT creates a DEFAULT CONSTRAINT at the same time as the column is created and then immediately removes that constraint: ALTER TABLE [dbo].[T1]    ADD [C1] INT NOT NULL,         CONSTRAINT [SD_T1_1df7a5f76cf44bb593506d05ff9a1e2b] DEFAULT 0 FOR [C1];ALTER TABLE [dbo].[T1] DROP CONSTRAINT [SD_T1_1df7a5f76cf44bb593506d05ff9a1e2b]; You can then update the value as appropriate in a Post-Deployment script. Pretty cool! On the downside, you can only specify this option for the whole project, not for an individual table or even an individual column – I’m not sure that I’d want to turn this on for an entire project as it could hide problems that a failed deployment would highlight, in other words smart defaults could be seen to be “papering over the cracks”. If you think that should be improved go and vote (and leave a comment) at [SSDT] Allow us to specify Smart defaults per table or even per column. @Jamiet

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  • Is the SAN dying???

    - by RickHeiges
    Is the SAN dying? The reason that I ask this question is that MSFT has unleashed technologies this year that point in that direction Always ON Availability Groups shuns shared storage Windows 2012 has Storage Replication Technology that does not require a SAN Windows 2012 has Hyper-V Replica Technology that does not require a SAN PDW v2 continues to reinforce the approach to avoid shared storage I'm not saying that SAN technology does not have its place or does not have benefits inherent to the beast....(read more)

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  • Defaults for Exporting Data in Oracle SQL Developer

    - by thatjeffsmith
    I was testing a reported bug in SQL Developer today – so the bug I was looking for wasn’t there (YES!) but I found a different one (NO!) – and I was getting frustrated by having to check the same boxes over and over again. What I wanted was INSERT STATEMENTS to the CLIPBOARD. Not what I want! I’m always doing the same thing, over and over again. And I never go to FILE – that’s too permanent for my type of work. I either want stuff to the clipboard or to the worksheet. Surely there’s a way to tell SQL Developer how to behave? Oh yeah, check the preferences So you can set the defaults for this dialog. Go to: Tools – Preferences – Database – Utilities – Export Now I will always start with ‘INSERT’ and ‘Clipboard’ – woohoo! Now, I can also go INTO the preferences for each of the different formats to save me a few more clicks. I prefer pointy hats (^) for my delimiters, don’t you? So, spend a few minutes and set each of these to what you’re normally doing and save yourself a bunch of time going forward.

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  • SQL Server 2008 R2 Service Pack 2 CTP is available

    - by AaronBertrand
    You can download the Service Pack 2 CTP from the following URL: http://www.microsoft.com/en-us/download/details.aspx?id=29848 The build # is 10.50.3720. This service pack contains all of the fixes from Service Pack 1 & Cumulative Updates 1 through 5, and a couple of other minor fixes (a couple of SSRS bugs and a bug about an ALTER TABLE batch not being cached correctly). It does not include fixes from Service Pack 1 Cumulative Update #6, which I mentioned recently . You should *NOT* install this...(read more)

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  • Oracle Database 12c By Example – SQL Developer and Multitenant

    - by thatjeffsmith
    As you may have heard, Oracle Database 12c is now available. In addition to the binaries and docs going out, we also published a few new Oracle By Example (OBE) chapters. You can find those links here on our product page. Do you know who found these, practically the minute they were published? An enterprising DBA-extraordinaire who was just happening to be presenting at the ODTUG KScope13 conference in New Orleans. He thought it would be a good idea to download the new software over a hotel WIFI, install and create a new multitenant database, watch a few OBEs, and then demo that live for his ‘SQL Developer for DBAs‘ session. Pretty crazy, right? Well, he did it, and I was there to watch. Way cool. You can listen to @leight0nn tell his story in his own words via this ODTUG interview with @oraclenered. In case you’re too giddy to sit through the video, I’ll give you a preview – he succesfully cloned a pluggable database in about a minute with only a couple of clicks using Oracle SQL Developer 3.2.20.09 while connected to a 12c database.

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  • SQL Server Add Primary Key

    - by Derek D.
    Adding a primary key can be done either after a table is created, or at the same a table is created. It is important to note, that by default a primary key is clustered. This may or may not be the preferred method of creation. For more information on clustered vs non [...]

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  • SQL Server 2000 need to prevent logons whilst performing a backup for a side by side migration

    - by pigeon
    I'm looking for a way to prevent logons from occurring in order to take a full backup of a Database to migrate from its current SQL Server 2000 instance to a new SQL 2005 instance. A friend of mine suggested running a script which would put the DB into a rollback state. Not being a DBA my DDL is very poor and running a script that I don't understand may not be the best idea. One option which might be easier is to simply detach and copy, to the new server. Any suggestions would be greatly appreciated.

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  • High Performance SQL Views Using WITH(NOLOCK)

    - by gt0084e1
    Every now and then you find a simple way to make everything much faster. We often find customers creating data warehouses or OLAP cubes even though they have a relatively small amount of data (a few gigs) compared to their server memory. If you have more server memory than the size of your database or working set, nearly any aggregate query should run in a second or less. In some situations there may be high traffic on from the transactional application and SQL server may wait for several other queries to run before giving you your results. The purpose of this is make sure you don’t get two versions of the truth. In an ATM system, you want to give the bank balance after the withdrawal, not before or you may get a very unhappy customer. So by default databases are rightly very conservative about this kind of thing. Unfortunately this split-second precision comes at a cost. The performance of the query may not be acceptable by today’s standards because the database has to maintain locks on the server. Fortunately, SQL Server gives you a simple way to ask for the current version of the data without the pending transactions. To better facilitate reporting, you can create a view that includes these directives. CREATE VIEW CategoriesAndProducts AS SELECT * FROM dbo.Categories WITH(NOLOCK) INNER JOIN dbo.Products WITH(NOLOCK) ON dbo.Categories.CategoryID = dbo.Products.CategoryID In some cases quires that are taking minutes end up taking seconds. Much easier than moving the data to a separate database and it’s still pretty much real time give or take a few milliseconds. You’ve been warned not to use this for bank balances though. More from Data Stream

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  • SQL Server Manageability Series: how to change the default path of .cache files of a data collector? #sql #mdw #dba

    - by ssqa.net
    How to change the default path of .cache files of a data collector after the Management Data Warehouse (MDW has been setup? This was the question asked by one of the DBAs in a client's place, instantly I enquired that were there any folder specified while setting up the MDW and obvious answer was no as there were left default. This means all the .CACHE files are stored under %C\TEMP directory which may post out of disk space problem on the server where the MDW is setup to collect. Going back...(read more)

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  • A different interface for the Sql Server Reporting Service?

    - by AngryHacker
    I have a SQL Server 2005 SQL Reporting Services implementation. It seems that the only way to actually access the reports is for the users to use Internet Explorer. The web page uses an ActiveX control to do its printing (and probably other functions as well). Does SSRS have a different way to access its functionality via the web browser? Like maybe Java or HTML based? If so, how do I actually turn it on? The reason I am asking is because the security is being tightened and ActiveX controls will be banished, thus the users won't be able to print.

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  • MERGE gives better OUTPUT options

    - by Rob Farley
    MERGE is very cool. There are a ton of useful things about it – mostly around the fact that you can implement a ton of change against a table all at once. This is great for data warehousing, handling changes made to relational databases by applications, all kinds of things. One of the more subtle things about MERGE is the power of the OUTPUT clause. Useful for logging.   If you’re not familiar with the OUTPUT clause, you really should be – it basically makes your DML (INSERT/DELETE/UPDATE/MERGE) statement return data back to you. This is a great way of returning identity values from INSERT commands (so much better than SCOPE_IDENTITY() or the older (and worse) @@IDENTITY, because you can get lots of rows back). You can even use it to grab default values that are set using non-deterministic functions like NEWID() – things you couldn’t normally get back without running another query (or with a trigger, I guess, but that’s not pretty). That inserted table I referenced – that’s part of the ‘behind-the-scenes’ work that goes on with all DML changes. When you insert data, this internal table called inserted gets populated with rows, and then used to inflict the appropriate inserts on the various structures that store data (HoBTs – the Heaps or B-Trees used to store data as tables and indexes). When deleting, the deleted table gets populated. Updates get a matching row in both tables (although this doesn’t mean that an update is a delete followed by an inserted, it’s just the way it’s handled with these tables). These tables can be referenced by the OUTPUT clause, which can show you the before and after for any DML statement. Useful stuff. MERGE is slightly different though. With MERGE, you get a mix of entries. Your MERGE statement might be doing some INSERTs, some UPDATEs and some DELETEs. One of the most common examples of MERGE is to perform an UPSERT command, where data is updated if it already exists, or inserted if it’s new. And in a single operation too. Here, you can see the usefulness of the deleted and inserted tables, which clearly reflect the type of operation (but then again, MERGE lets you use an extra column called $action to show this). (Don’t worry about the fact that I turned on IDENTITY_INSERT, that’s just so that I could insert the values) One of the things I love about MERGE is that it feels almost cursor-like – the UPDATE bit feels like “WHERE CURRENT OF …”, and the INSERT bit feels like a single-row insert. And it is – but into the inserted and deleted tables. The operations to maintain the HoBTs are still done using the whole set of changes, which is very cool. And $action – very convenient. But as cool as $action is, that’s not the point of my post. If it were, I hope you’d all be disappointed, as you can’t really go near the MERGE statement without learning about it. The subtle thing that I love about MERGE with OUTPUT is that you can hook into more than just inserted and deleted. Did you notice in my earlier query that my source table had a ‘src’ field, that wasn’t used in the insert? Normally, this would be somewhat pointless to include in my source query. But with MERGE, I can put that in the OUTPUT clause. This is useful stuff, particularly when you’re needing to audit the changes. Suppose your query involved consolidating data from a number of sources, but you didn’t need to insert that into the actual table, just into a table for audit. This is now very doable, either using the INTO clause of OUTPUT, or surrounding the whole MERGE statement in brackets (parentheses if you’re American) and using a regular INSERT statement. This is also doable if you’re using MERGE to just do INSERTs. In case you hadn’t realised, you can use MERGE in place of an INSERT statement. It’s just like the UPSERT-style statement we’ve just seen, except that we want nothing to match. That’s easy to do, we just use ON 1=2. This is obviously more convoluted than a straight INSERT. And it’s slightly more effort for the database engine too. But, if you want the extra audit capabilities, the ability to hook into the other source columns is definitely useful. Oh, and before people ask if you can also hook into the target table’s columns... Yes, of course. That’s what deleted and inserted give you.

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  • Q&amp;A: Will my favourite ORM Foo work with SQL Azure?

    - by Eric Nelson
    short answer: Quite probably, as SQL Azure is very similar to SQL Server longer answer: Object Relational Mappers (ORMs) that work with SQL Server are likely but not guaranteed to work with SQL Azure. The differences between the RDBMS versions are small – but may cause problems, for example in tools used to create the mapping between objects and tables or in generated SQL from the ORM which expects “certain things” :-) More specifically: ADO.NET Entity Framework / LINQ to Entities can be used with SQL Azure, but the Visual Studio designer does not currently work. You will need to point the designer at a version of your database running of SQL Server to create the mapping, then change the connection details to run against SQL Azure. LINQ to SQL has similar issues to ADO.NET Entity Framework above NHibernate can be used against SQL Azure DevExpress XPO supports SQL Azure from version 9.3 DataObjects.Net supports SQL Azure Open Access from Telerik works “seamlessly”  - their words not mine :-) The list above is by no means comprehensive – please leave a comment with details of other ORMs that work (or do not work) with SQL Azure. Related Links: General guidelines and limitations of SQL Azure SQL Azure vs SQL Server

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  • A little on speaking and evaluations...

    - by AaronBertrand
    Buck Woody ( blog | twitter ) just published a great post on session evaluations , and a lot of his points hit home for me. The premise is that the evaluations are not really meant for the attendee or the event organizers, but so that the speaker can get better and make the next session better. In light of this, at least in my opinion, the existing evaluation forms (and the way attendees tend to fill them out) do not achieve this at all. It may be a little more work for events to generate a more...(read more)

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  • Denali CTP3 - Semantic Search 2 (Lots of documents)

    - by sqlartist
    Hi again, I thought I would improve on the previous post by actually putting a decent about of content into the Filetable - this time I used the opensource DMOZ Health document repository which contains 5,880 files inside 220 folders. The files are all html and are pretty small in size. The entire document collection is about 120Mb unzipped and 30Mb zipped. If any one is interested in testing this collection drop me a note and I will upload the dmoz_health repository archive to Skydrive. This time...(read more)

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  • T-SQL Tuesday #19: Blind Spots

    - by merrillaldrich
    A while ago I wrote a post, Visualize Disaster , prompted by a real incident we had at my office. Fortunately we came through it OK from a business point of view, but I took away an important lesson: it’s very easy, whether your organization and your team is savvy about disaster recovery or not, to have significant blind spots with regard to recovery in the face of some large, unexpected outage. We have very clear direction and decent budgets to work with, and the safety and recoverability of applications...(read more)

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  • Scream if you want to go faster

    - by simonsabin
    My session for 24hrs of pass on High Performance functions will be starting at 11:00 GMT thats migdnight for folks in the UK. To attend follow this link https://www.livemeeting.com/cc/8000181573/join?id=N5Q8S7&role=attend&pw=d2%28_KmN3r The rest of the sessions can be found here http://www.sqlpass.org/24hours/2010/Sessions/ChronologicalOrder.aspx So far the sessions have been great so no pressure :( See you there in 4.5 hrs...(read more)

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  • T-SQL (SCD) Slowly Changing Dimension Type 2 using a merge statement

    - by AtulThakor
    Working on stored procedure recently which loads records into a data warehouse I found that the existing record was being expired using an update statement followed by an insert to add the new active record. Playing around with the merge statement you can actually expire the current record and insert a new record within one clean statement. This is how the statement works, we do the normal merge statement to insert a record when there is no match, if we match the record we update the existing record by expiring it and deactivating. At the end of the merge statement we use the output statement to output the staging values for the update,  we wrap the whole merge statement within an insert statement and add new rows for the records which we inserted. I’ve added the full script at the bottom so you can paste it and play around.   1: INSERT INTO ExampleFactUpdate 2: (PolicyID, 3: Status) 4: SELECT -- these columns are returned from the output statement 5: PolicyID, 6: Status 7: FROM 8: ( 9: -- merge statement on unique id in this case Policy_ID 10: MERGE dbo.ExampleFactUpdate dp 11: USING dbo.ExampleStag s 12: ON dp.PolicyID = s.PolicyID 13: WHEN NOT MATCHED THEN -- when we cant match the record we insert a new record record and this is all that happens 14: INSERT (PolicyID,Status) 15: VALUES (s.PolicyID, s.Status) 16: WHEN MATCHED --if it already exists 17: AND ExpiryDate IS NULL -- and the Expiry Date is null 18: THEN 19: UPDATE 20: SET 21: dp.ExpiryDate = getdate(), --we set the expiry on the existing record 22: dp.Active = 0 -- and deactivate the existing record 23: OUTPUT $Action MergeAction, s.PolicyID, s.Status -- the output statement returns a merge action which can 24: ) MergeOutput -- be insert/update/delete, on our example where a record has been updated (or expired in our case 25: WHERE -- we'll filter using a where clause 26: MergeAction = 'Update'; -- here   Complete source for example 1: if OBJECT_ID('ExampleFactUpdate') > 0 2: drop table ExampleFactUpdate 3:  4: Create Table ExampleFactUpdate( 5: ID int identity(1,1), 3: go 6: PolicyID varchar(100), 7: Status varchar(100), 8: EffectiveDate datetime default getdate(), 9: ExpiryDate datetime, 10: Active bit default 1 11: ) 12:  13:  14: insert into ExampleFactUpdate( 15: PolicyID, 16: Status) 17: select 18: 1, 19: 'Live' 20:  21: /*Create Staging Table*/ 22: if OBJECT_ID('ExampleStag') > 0 23: drop table ExampleStag 24: go 25:  26: /*Create example fact table */ 27: Create Table ExampleStag( 28: PolicyID varchar(100), 29: Status varchar(100)) 30:  31: --add some data 32: insert into ExampleStag( 33: PolicyID, 34: Status) 35: select 36: 1, 37: 'Lapsed' 38: union all 39: select 40: 2, 41: 'Quote' 42:  43: select * 44: from ExampleFactUpdate 45:  46: select * 47: from ExampleStag 48:  49:  50: INSERT INTO ExampleFactUpdate 51: (PolicyID, 52: Status) 53: SELECT -- these columns are returned from the output statement 54: PolicyID, 55: Status 56: FROM 57: ( 58: -- merge statement on unique id in this case Policy_ID 59: MERGE dbo.ExampleFactUpdate dp 60: USING dbo.ExampleStag s 61: ON dp.PolicyID = s.PolicyID 62: WHEN NOT MATCHED THEN -- when we cant match the record we insert a new record record and this is all that happens 63: INSERT (PolicyID,Status) 64: VALUES (s.PolicyID, s.Status) 65: WHEN MATCHED --if it already exists 66: AND ExpiryDate IS NULL -- and the Expiry Date is null 67: THEN 68: UPDATE 69: SET 70: dp.ExpiryDate = getdate(), --we set the expiry on the existing record 71: dp.Active = 0 -- and deactivate the existing record 72: OUTPUT $Action MergeAction, s.PolicyID, s.Status -- the output statement returns a merge action which can 73: ) MergeOutput -- be insert/update/delete, on our example where a record has been updated (or expired in our case 74: WHERE -- we'll filter using a where clause 75: MergeAction = 'Update'; -- here 76:  77:  78: select * 79: from ExampleFactUpdate 80: 

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  • Make huge space savings by using SPARSE columns

    - by simonsabin
    I’ve blogged before about Getting more than 1024 columns on a table , this is done by using sparse columns. Whilst this is potentially useful for people with insane table designs, sparse columns aren’t just for this. My experience over the past few years has shown that sparse columns are useful for almost all databases when you have columns that are largely null i.e. sparse. A recent client was able to reduce the size of the table by 60% by changing columns to sparse. The way this is achieved is...(read more)

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  • Wait Statistics in Microsoft SQL Server

    - by KKline
    When it comes to troubleshooting in relational databases, there's no better place to start than wait statistics. In a nutshell, a wait statistic is an internal counter that tells you how long the database spent waiting for a particular resource, activity, or process. Since wait statistics are categorized by type, one look will quickly tell the variety of problem that needs your attention, assuming you know meaning for Microsoft's lingo for each wait type....(read more)

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