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  • Returning Identity Value in SQL Server: @@IDENTITY Vs SCOPE_IDENTITY Vs IDENT_CURRENT

    - by Arefin Ali
    We have some common misconceptions on returning the last inserted identity value from tables. To return the last inserted identity value we have options to use @@IDENTITY or SCOPE_IDENTITY or IDENT_CURRENT function depending on the requirement but it will be a real mess if anybody uses anyone of these functions without knowing exact purpose. So here I want to share my thoughts on this. @@IDENTITY, SCOPE_IDENTITY and IDENT_CURRENT are almost similar functions in terms of returning identity value. They all return values that are inserted into an identity column. Earlier in SQL Server 7 we used to use @@IDENTITY to return the last inserted identity value because those days we don’t have functions like SCOPE_IDENTITY or IDENT_CURRENT but now we have these three functions. So let’s check out which one responsible for what. IDENT_CURRENT returns the last inserted identity value in a particular table. It never depends on a connection or the scope of the insert statement. IDENT_CURRENT function takes a table name as parameter. Here is the syntax to get the last inserted identity value in a particular table using IDENT_CURRENT function. SELECT IDENT_CURRENT('Employee') Both the @@IDENTITY and SCOPE_IDENTITY return the last inserted identity value created in any table in the current session. But there is little difference between these two i.e. SCOPE_IDENTITY returns value inserted only within the current scope whereas @@IDENTITY is not limited to any particular scope. Here are the syntaxes to get the last inserted identity value using these functions SELECT @@IDENTITY SELECT SCOPE_IDENTITY() Now let’s have a look at the following example. Suppose I have two tables called Employee and EmployeeLog. CREATE TABLE Employee ( EmpId NUMERIC(18, 0) IDENTITY(1,1) NOT NULL, EmpName VARCHAR(100) NOT NULL, EmpSal FLOAT NOT NULL, DateOfJoining DATETIME NOT NULL DEFAULT(GETDATE()) ) CREATE TABLE EmployeeLog ( EmpId NUMERIC(18, 0) IDENTITY(1,1) NOT NULL, EmpName VARCHAR(100) NOT NULL, EmpSal FLOAT NOT NULL, DateOfJoining DATETIME NOT NULL DEFAULT(GETDATE()) ) I have an insert trigger defined on the table Employee which inserts a new record in the EmployeeLog whenever a record insert in the Employee table. So Suppose I insert a new record in the Employee table using following statement: INSERT INTO Employee (EmpName,EmpSal) VALUES ('Arefin','1') The trigger will be fired automatically and insert a record in EmployeeLog. Here the scope of the insert statement and the trigger are different. In this situation if I retrieve last inserted identity value using @@IDENTITY, it will simply return the identity value from the EmployeeLog because it’s not limited to a particular scope. Now if I want to get the Employee table’s identity value then I need to use SCOPE_IDENTITY in this scenario. So the moral is always use SCOPE_IDENTITY to return the identity value of a recently created record in a sql statement or stored procedure. It’s safe and ensures bug free code.

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  • Returning Identity Value in SQL Server: @@IDENTITY Vs SCOPE_IDENTITY Vs IDENT_CURRENT

    - by Arefin Ali
    We have some common misconceptions on returning the last inserted identity value from tables. To return the last inserted identity value we have options to use @@IDENTITY or SCOPE_IDENTITY or IDENT_CURRENT function depending on the requirement but it will be a real mess if anybody uses anyone of these functions without knowing exact purpose. So here I want to share my thoughts on this. @@IDENTITY, SCOPE_IDENTITY and IDENT_CURRENT are almost similar functions in terms of returning identity value. They all return values that are inserted into an identity column. Earlier in SQL Server 7 we used to use @@IDENTITY to return the last inserted identity value because those days we don’t have functions like SCOPE_IDENTITY or IDENT_CURRENT but now we have these three functions. So let’s check out which one responsible for what. IDENT_CURRENT returns the last inserted identity value in a particular table. It never depends on a connection or the scope of the insert statement. IDENT_CURRENT function takes a table name as parameter. Here is the syntax to get the last inserted identity value in a particular table using IDENT_CURRENT function. SELECT IDENT_CURRENT('Employee') Both the @@IDENTITY and SCOPE_IDENTITY return the last inserted identity value created in any table in the current session. But there is little difference between these two i.e. SCOPE_IDENTITY returns value inserted only within the current scope whereas @@IDENTITY is not limited to any particular scope. Here are the syntaxes to get the last inserted identity value using these functions SELECT @@IDENTITYSELECT SCOPE_IDENTITY() Now let’s have a look at the following example. Suppose I have two tables called Employee and EmployeeLog. CREATE TABLE Employee( EmpId NUMERIC(18, 0) IDENTITY(1,1) NOT NULL, EmpName VARCHAR(100) NOT NULL, EmpSal FLOAT NOT NULL, DateOfJoining DATETIME NOT NULL DEFAULT(GETDATE()))CREATE TABLE EmployeeLog( EmpId NUMERIC(18, 0) IDENTITY(1,1) NOT NULL, EmpName VARCHAR(100) NOT NULL, EmpSal FLOAT NOT NULL, DateOfJoining DATETIME NOT NULL DEFAULT(GETDATE())) I have an insert trigger defined on the table Employee which inserts a new record in the EmployeeLog whenever a record insert in the Employee table. So Suppose I insert a new record in the Employee table using following statement: INSERT INTO Employee (EmpName,EmpSal) VALUES ('Arefin','1') The trigger will be fired automatically and insert a record in EmployeeLog. Here the scope of the insert statement and the trigger are different. In this situation if I retrieve last inserted identity value using @@IDENTITY, it will simply return the identity value from the EmployeeLog because it’s not limited to a particular scope. Now if I want to get the Employee table’s identity value then I need to use SCOPE_IDENTITY in this scenario. So the moral is always use SCOPE_IDENTITY to return the identity value of a recently created record in a sql statement or stored procedure. It’s safe and ensures bug free code.

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  • SQL SERVER – Example of Performance Tuning for Advanced Users with DB Optimizer

    - by Pinal Dave
    Performance tuning is such a subject that everyone wants to master it. In beginning everybody is at a novice level and spend lots of time learning how to master the art of performance tuning. However, as we progress further the tuning of the system keeps on getting very difficult. I have understood in my early career there should be no need of ego in the technology field. There are always better solutions and better ideas out there and we should not resist them. Instead of resisting the change and new wave I personally adopt it. Here is a similar example, as I personally progress to the master level of performance tuning, I face that it is getting harder to come up with optimal solutions. In such scenarios I rely on various tools to teach me how I can do things better. Once I learn about tools, I am often able to come up with better solutions when I face the similar situation next time. A few days ago I had received a query where the user wanted to tune it further to get the maximum out of the performance. I have re-written the similar query with the help of AdventureWorks sample database. SELECT * FROM HumanResources.Employee e INNER JOIN HumanResources.EmployeeDepartmentHistory edh ON e.BusinessEntityID = edh.BusinessEntityID INNER JOIN HumanResources.Shift s ON edh.ShiftID = s.ShiftID; User had similar query to above query was used in very critical report and wanted to get best out of the query. When I looked at the query – here were my initial thoughts Use only column in the select statements as much as you want in the application Let us look at the query pattern and data workload and find out the optimal index for it Before I give further solutions I was told by the user that they need all the columns from all the tables and creating index was not allowed in their system. He can only re-write queries or use hints to further tune this query. Now I was in the constraint box – I believe * was not a great idea but if they wanted all the columns, I believe we can’t do much besides using *. Additionally, if I cannot create a further index, I must come up with some creative way to write this query. I personally do not like to use hints in my application but there are cases when hints work out magically and gives optimal solutions. Finally, I decided to use Embarcadero’s DB Optimizer. It is a fantastic tool and very helpful when it is about performance tuning. I have previously explained how it works over here. First open DBOptimizer and open Tuning Job from File >> New >> Tuning Job. Once you open DBOptimizer Tuning Job follow the various steps indicates in the following diagram. Essentially we will take our original script and will paste that into Step 1: New SQL Text and right after that we will enable Step 2 for Generating Various cases, Step 3 for Detailed Analysis and Step 4 for Executing each generated case. Finally we will click on Analysis in Step 5 which will generate the report detailed analysis in the result pan. The detailed pan looks like. It generates various cases of T-SQL based on the original query. It applies various hints and available hints to the query and generate various execution plans of the query and displays them in the resultant. You can clearly notice that original query had a cost of 0.0841 and logical reads about 607 pages. Whereas various options which are just following it has different execution cost as well logical read. There are few cases where we have higher logical read and there are few cases where as we have very low logical read. If we pay attention the very next row to original query have Merge_Join_Query in description and have lowest execution cost value of 0.044 and have lowest Logical Reads of 29. This row contains the query which is the most optimal re-write of the original query. Let us double click over it. Here is the query: SELECT * FROM HumanResources.Employee e INNER JOIN HumanResources.EmployeeDepartmentHistory edh ON e.BusinessEntityID = edh.BusinessEntityID INNER JOIN HumanResources.Shift s ON edh.ShiftID = s.ShiftID OPTION (MERGE JOIN) If you notice above query have additional hint of Merge Join. With the help of this Merge Join query hint this query is now performing much better than before. The entire process takes less than 60 seconds. Please note that it the join hint Merge Join was optimal for this query but it is not necessary that the same hint will be helpful in all the queries. Additionally, if the workload or data pattern changes the query hint of merge join may be no more optimal join. In that case, we will have to redo the entire exercise once again. This is the reason I do not like to use hints in my queries and I discourage all of my users to use the same. However, if you look at this example, this is a great case where hints are optimizing the performance of the query. It is humanly not possible to test out various query hints and index options with the query to figure out which is the most optimal solution. Sometimes, we need to depend on the efficiency tools like DB Optimizer to guide us the way and select the best option from the suggestion provided. Let me know what you think of this article as well your experience with DB Optimizer. Please leave a comment. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Joins, SQL Optimization, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Upgrading from 2005 to R2

    - by DavidWimbush
    We're about to take the plunge and upgrade our servers from SQL 2005 to SQL 2008 R2. Real world accounts of people upgrading to R2 are a bit hard to find so I thought it might be useful to blog what happens. (I don't count marketing 'case studies' that just say stuff like "The process was effortless and the upgrade will pay for itself by the end the week.") We're using the database engine, Analysis Services and Reporting Services so upgrading by a major version number was looking a bit daunting. I wasn't expecting much trouble on the engine side of things but, as most of the action in 2008 and R2 appears to have been on the Reporting and BI front, I expected to have quite a bit of work to do. But our testing so far has been one nice surprise after another: The 2005 backups restore cleanly onto R2. R2's BI Studio upgraded the Reporting and Analysis Services solutions without any issues. The cubes all deployed and processed just fine. R2 BI Studio interacts fine with TFS 2008 version control. I'll blog some more as things develop.  

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  • SQL SERVER – Fundamentals of Columnstore Index

    - by pinaldave
    There are two kind of storage in database. Row Store and Column Store. Row store does exactly as the name suggests – stores rows of data on a page – and column store stores all the data in a column on the same page. These columns are much easier to search – instead of a query searching all the data in an entire row whether the data is relevant or not, column store queries need only to search much lesser number of the columns. This means major increases in search speed and hard drive use. Additionally, the column store indexes are heavily compressed, which translates to even greater memory and faster searches. I am sure this looks very exciting and it does not mean that you convert every single index from row store to column store index. One has to understand the proper places where to use row store or column store indexes. Let us understand in this article what is the difference in Columnstore type of index. Column store indexes are run by Microsoft’s VertiPaq technology. However, all you really need to know is that this method of storing data is columns on a single page is much faster and more efficient. Creating a column store index is very easy, and you don’t have to learn new syntax to create them. You just need to specify the keyword “COLUMNSTORE” and enter the data as you normally would. Keep in mind that once you add a column store to a table, though, you cannot delete, insert or update the data – it is READ ONLY. However, since column store will be mainly used for data warehousing, this should not be a big problem. You can always use partitioning to avoid rebuilding the index. A columnstore index stores each column in a separate set of disk pages, rather than storing multiple rows per page as data traditionally has been stored. The difference between column store and row store approaches is illustrated below: In case of the row store indexes multiple pages will contain multiple rows of the columns spanning across multiple pages. In case of column store indexes multiple pages will contain multiple single columns. This will lead only the columns needed to solve a query will be fetched from disk. Additionally there is good chance that there will be redundant data in a single column which will further help to compress the data, this will have positive effect on buffer hit rate as most of the data will be in memory and due to same it will not need to be retrieved. Let us see small example of how columnstore index improves the performance of the query on a large table. As a first step let us create databaseset which is large enough to show performance impact of columnstore index. The time taken to create sample database may vary on different computer based on the resources. USE AdventureWorks GO -- Create New Table CREATE TABLE [dbo].[MySalesOrderDetail]( [SalesOrderID] [int] NOT NULL, [SalesOrderDetailID] [int] NOT NULL, [CarrierTrackingNumber] [nvarchar](25) NULL, [OrderQty] [smallint] NOT NULL, [ProductID] [int] NOT NULL, [SpecialOfferID] [int] NOT NULL, [UnitPrice] [money] NOT NULL, [UnitPriceDiscount] [money] NOT NULL, [LineTotal] [numeric](38, 6) NOT NULL, [rowguid] [uniqueidentifier] NOT NULL, [ModifiedDate] [datetime] NOT NULL ) ON [PRIMARY] GO -- Create clustered index CREATE CLUSTERED INDEX [CL_MySalesOrderDetail] ON [dbo].[MySalesOrderDetail] ( [SalesOrderDetailID]) GO -- Create Sample Data Table -- WARNING: This Query may run upto 2-10 minutes based on your systems resources INSERT INTO [dbo].[MySalesOrderDetail] SELECT S1.* FROM Sales.SalesOrderDetail S1 GO 100 Now let us do quick performance test. I have kept STATISTICS IO ON for measuring how much IO following queries take. In my test first I will run query which will use regular index. We will note the IO usage of the query. After that we will create columnstore index and will measure the IO of the same. -- Performance Test -- Comparing Regular Index with ColumnStore Index USE AdventureWorks GO SET STATISTICS IO ON GO -- Select Table with regular Index SELECT ProductID, SUM(UnitPrice) SumUnitPrice, AVG(UnitPrice) AvgUnitPrice, SUM(OrderQty) SumOrderQty, AVG(OrderQty) AvgOrderQty FROM [dbo].[MySalesOrderDetail] GROUP BY ProductID ORDER BY ProductID GO -- Table 'MySalesOrderDetail'. Scan count 1, logical reads 342261, physical reads 0, read-ahead reads 0. -- Create ColumnStore Index CREATE NONCLUSTERED COLUMNSTORE INDEX [IX_MySalesOrderDetail_ColumnStore] ON [MySalesOrderDetail] (UnitPrice, OrderQty, ProductID) GO -- Select Table with Columnstore Index SELECT ProductID, SUM(UnitPrice) SumUnitPrice, AVG(UnitPrice) AvgUnitPrice, SUM(OrderQty) SumOrderQty, AVG(OrderQty) AvgOrderQty FROM [dbo].[MySalesOrderDetail] GROUP BY ProductID ORDER BY ProductID GO It is very clear from the results that query is performance extremely fast after creating ColumnStore Index. The amount of the pages it has to read to run query is drastically reduced as the column which are needed in the query are stored in the same page and query does not have to go through every single page to read those columns. If we enable execution plan and compare we can see that column store index performance way better than regular index in this case. Let us clean up the database. -- Cleanup DROP INDEX [IX_MySalesOrderDetail_ColumnStore] ON [dbo].[MySalesOrderDetail] GO TRUNCATE TABLE dbo.MySalesOrderDetail GO DROP TABLE dbo.MySalesOrderDetail GO In future posts we will see cases where Columnstore index is not appropriate solution as well few other tricks and tips of the columnstore index. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Index, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Date and Time Support in SQL Server 2008

    - by Aamir Hasan
      Using the New Date and Time Data Types Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} 1.       The new date and time data types in SQL Server 2008 offer increased range and precision and are ANSI SQL compatible. 2.       Separate date and time data types minimize storage space requirements for applications that need only date or time information. Moreover, the variable precision of the new time data type increases storage savings in exchange for reduced accuracy. 3.       The new data types are mostly compatible with the original date and time data types and use the same Transact-SQL functions. 4.       The datetimeoffset data type allows you to handle date and time information in global applications that use data that originates from different time zones. SELECT c.name, p.* FROM politics pJOIN country cON p.country = c.codeWHERE YEAR(Independence) < 1753ORDER BY IndependenceGO8.    Highlight the SELECT statement and click Execute ( ) to show the use of some of the date functions.T-SQLSELECT c.name AS [Country Name],        CONVERT(VARCHAR(12), p.Independence, 107) AS [Independence Date],       DATEDIFF(YEAR, p.Independence, GETDATE()) AS [Years Independent (appox)],       p.GovernmentFROM politics pJOIN country cON p.country = c.codeWHERE YEAR(Independence) < 1753ORDER BY IndependenceGO10.    Select the SET DATEFORMAT statement and click Execute ( ) to change the DATEFORMAT to day-month-year.T-SQLSET DATEFORMAT dmyGO11.    Select the DECLARE and SELECT statements and click Execute ( ) to show how the datetime and datetime2 data types interpret a date literal.T-SQLSET DATEFORMAT dmyDECLARE @dt datetime = '2008-12-05'DECLARE @dt2 datetime2 = '2008-12-05'SELECT MONTH(@dt) AS [Month-Datetime], DAY(@dt)     AS [Day-Datetime]SELECT MONTH(@dt2) AS [Month-Datetime2], DAY(@dt2)     AS [Day-Datetime2]GO12.    Highlight the DECLARE and SELECT statements and click Execute ( ) to use integer arithmetic on a datetime variable.T-SQLDECLARE @dt datetime = '2008-12-05'SELECT @dt + 1GO13.    Highlight the DECLARE and SELECT statements and click Execute ( ) to show how integer arithmetic is not allowed for datetime2 variables.T-SQLDECLARE @dt2 datetime = '2008-12-05'SELECT @dt2 + 1GO14.    Highlight the DECLARE and SELECT statements and click Execute ( ) to show how to use DATE functions to do simple arithmetic on datetime2 variables.T-SQLDECLARE @dt2 datetime2(7) = '2008-12-05'SELECT DATEADD(d, 1, @dt2)GO15.    Highlight the DECLARE and SELECT statements and click Execute ( ) to show how the GETDATE function can be used with both datetime and datetime2 data types.T-SQLDECLARE @dt datetime = GETDATE();DECLARE @dt2 datetime2(7) = GETDATE();SELECT @dt AS [GetDate-DateTime], @dt2 AS [GetDate-DateTime2]GO16.    Draw attention to the values returned for both columns and how they are equal.17.    Highlight the DECLARE and SELECT statements and click Execute ( ) to show how the SYSDATETIME function can be used with both datetime and datetime2 data types.T-SQLDECLARE @dt datetime = SYSDATETIME();DECLARE @dt2 datetime2(7) = SYSDATETIME();SELECT @dt AS [Sysdatetime-DateTime], @dt2     AS [Sysdatetime-DateTime2]GO18.    Draw attention to the values returned for both columns and how they are different.Programming Global Applications with DateTimeOffset 2.    If you have not previously created the SQLTrainingKitDB database while completing another demo in this training kit, highlight the CREATE DATABASE statement and click Execute ( ) to do so now.T-SQLCREATE DATABASE SQLTrainingKitDBGO3.    Select the USE and CREATE TABLE statements and click Execute ( ) to create table datetest in the SQLTrainingKitDB database.T-SQLUSE SQLTrainingKitDBGOCREATE TABLE datetest (  id integer IDENTITY PRIMARY KEY,  datetimecol datetimeoffset,  EnteredTZ varchar(40)); Reference:http://www.microsoft.com/downloads/details.aspx?FamilyID=E9C68E1B-1E0E-4299-B498-6AB3CA72A6D7&displaylang=en   

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  • How to configure Apache to let PHP handle OPTIONS HTTP requests?

    - by Robin Berjon
    In order to set up a proper test suite for CORS (cross-domain requests) I need to be able to handle the HTTP OPTIONS method directly from script. I therefore have a simple PHP script that detects the OPTIONS method, and reacts accordingly by outputting some specific headers. The PHP side is not a problem. If I use curl to issue GET/POST/HEAD/PUT/etc. requests they all go to the script and it clearly handles them fine. If I issue an OPTIONS request however, it never reaches the script: Apache immediately replies listing a set of methods that it believes to be appropriate for this resource. I can tell that the script isn't run (no logging, none of its output makes it to the response, etc.). I've been going through the Apache configuration, have made sure no applicable .htaccess is in the way, I've tweaked a bunch of things such as Limit/LimitExcept directives, but I can't get it to change its behaviour. I've also tried to find information on a technique from my youth that could have helped here: NPH (non-parsed headers) scripts; but apparently that has now disappeared (at least, I can't find any recent information about it that works). So the question is: how do I tweak Apache's configuration so that it will let my script handle OPTIONS?

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  • Have SSIS' differing type systems ever caused you problems?

    - by jamiet
    One thing that has always infuriated me about SSIS is the fact that every package has three different type systems; to give you an idea of what I am talking about consider the following: The SSIS dataflow's type system is made up of types called DT_*  (e.g. DT_STR, DT_I4) The SSIS variable type system is based on .Net datatypes (e.g. String, Int32) The types available for Execute SQL Task's parameters are based on something else - I don't exactly know what (e.g. VARCHAR, LONG) Speaking euphemistically ... this is not an optimum situation (were I not speaking euphemistically I would be a lot ruder) and hence I have submitted a suggestion to Connect at [SSIS] Consolidate three type systems into one requesting that it be remedied. This accompanying blog post is not however a request for votes (though that would be nice); the reason is actually subtler than that. Let me explain. I have been submitting bugs and suggestions pertaining to SSIS for years and have, so far, submitted over 200 Connect items. If that experience has taught me anything it is this - Connect items are not generally actioned because they are considered "nice to have". No, SSIS Connect items get actioned because they cause customers grief and if I am perfectly honest I must admit that, other than being a bit gnarly, SSIS' three type system architecture has never knowingly caused me any significant problems. The reason for this blog post is to ask if any reader out there has ever encountered any problems on account of SSIS' three type systems or have you, like me, never found them to be a problem? Errors or performance degredation caused by implicit type conversions would, I believe, present a strong case for getting this situation remedied in a future version of SSIS so if you HAVE encountered such problems I would encourage you to leave a comment on the Connect submission accordingly. Let me know in the comments too - I would be interested to hear others' opinions on this. @Jamiet

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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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  • 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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  • What could cause my LAN Pings be greater than 100ms?

    - by James Holland
    I have 2 servers (Both: Windows Server 2008, Dual Xeon 2.8Ghz, 32GB RAM, 8 x 15k SAS Drives). One of them is a DC / Web server / Exchange Server, the other is a SQL Server (2008). I have a 48 port Netgear GS748T Gigabit switch. When I ping from server to server, I get ping times <1ms, great, but when I ping from a PC, I get varying pings from the occasional <1ms to 500ms!! If I log into either server and look at Task Manager, CPU usage peaks at 20%, memory usage is 100%, but I am led to believe this is normal as Exchange will just use as much as you have, and release it when requested. Network usage peaks at 1%. I really don't understand how the ping can vary that much. I know I am giving very little info, but this is all I know, I apologise, but can anyone help? In response to question, I have pinged by both IP address and hostname, no difference in ping times.

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  • bad request error 400 while using python requests.post function

    - by Toussah
    I'm trying to make a simple post request via the requests library of Python and I get a bad request error (400) while my url is supposedly correct since I can use it to perform a get. I'm very new in REST requests, I read many tutorials and documentation but I guess there are still things I don't get so my error could be basic. Maybe a lack of understanding on the type of url I'm supposed to send via POST. Here my code : import requests v_username = "username" v_password = "password" v_headers = {'content-type':'application/rdf+xml'} url = 'https://my.url' params = {'param': 'val_param'} payload = {'data': 'my_data'} r = requests.post(url, params = params, auth=(v_username, v_password), data=payload, headers=v_headers, verify=False) print r I used the example of the requests documentation.

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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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  • SQL Solstice

    - by andyleonard
    Introduction My friends in North Carolina have decided to create a new event called SQL Solstice . Details: 18 - 20 Aug 2011 Holiday Inn Brownstone & Conference Center 1707 Hillsborough Street - Raleigh, NC 27605 Toll Free 800-331-7919 18 Aug - A Day of Deep Dives ($259) Day-long presentations delivered by folks with real-world, hands-on experience. Louis Davidson on Database Design Andrew Kelly on Performance Tuning Jessica M. Moss on Reporting Services Ed Wilson on Powershell (me) on SSIS 19...(read more)

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  • The perils of double-dash comments [T-SQL]

    - by jamiet
    I was checking my Twitter feed on my way in to work this morning and was alerted to an interesting blog post by Valentino Vranken that highlights a problem regarding the OLE DB Source in SSIS. In short, using double-dash comments in SQL statements within the OLE DB Source can cause unexpected results. It really is quite an important read if you’re developing SSIS packages so head over to SSIS OLE DB Source, Parameters And Comments: A Dangerous Mix! and be educated. Note that the problem is solved in SSIS2012 and Valentino explains exactly why. If reading Valentino’s post has switched your brain into “learn mode” perhaps also check out my post SSIS: SELECT *... or select from a dropdown in an OLE DB Source component? which highlights another issue to be aware of when using the OLE DB Source. As I was reading Valentino’s post I was reminded of a slidedeck by Chris Adkin entitled T-SQL Coding Guidelines where he recommends never using double-dash comments: That’s good advice! @Jamiet

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  • How To Find Reasons of Why Site Goes Online/Offline

    - by HollerTrain
    Seems today a website I manage has been going online and offline throughout the entire day. I have no idea what is causing the issue so I am seeking guidance on where to start. It is a Wordpress based site. So here is what I DO know: I use a program that pings the server every minute and when the server is not responding me it emails me, so I can know exactly when the site is online and offline. The site between 8pm to 12pm 12.28, and around the 1a hour early morning 12.29 (New York City timezone, and all times below are in same timezone). At the time of the ups/downs I see a lot of strain on the memory usage. Look at the load average when the site is going online/offline (http://screencast.com/t/BRlfXkqrbJII). Then I ran this command to restart http (http://screencast.com/t/usVtYWZ2Qi) and the memory usage then goes down to this (http://screencast.com/t/VdTIy3bgZiQB). An hour after I restarted http, the site then went offline/online so restarting the http didn't do much help. When the site is going offline/online, I ran the top command and get this (http://screencast.com/t/zEwr7YQj3). Here is a top command when the site is at it's lowest (http://screencast.com/t/eaMfha9lbT - so this would be dubbged "normal"). Here is a bandwidth report (http://screencast.com/t/AS0h2CH1Gypq). The traffic doesn't seem to be that much (http://screencast.com/t/s7hrWNNic1K), but looking at my times the site is going up/down this may be one of the reasons? I have the dvp Nitro package at Media Temple (http://mediatemple.net/webhosting/nitro/). So at this point I would request some help in trying to figure out what the cause of this is, and how I can go about pinpointing this issue. ANY HELP is greatly appreciated.

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  • SQL SERVER Subquery or Join Various Options SQL Server Engine knows the Best

    This is followup post of my earlier article SQL SERVER Convert IN to EXISTS Performance Talk, after reading all the comments I have received I felt that I could write more on the same subject to clear few things out. First let us run following four queries, all of them are giving exactly [...]...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • How to select the value of the xsi:type attribute in SQL Server?

    - by kralizek
    Considering this xml document: DECLARE @X XML (DOCUMENT search.SearchParameters) = '< parameters xmlns="http://www.educations.com/Search/Parameters.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> < parameter xsi:type="category" categoryID="38" /> < /parameters>'; I'd like to access the value of the attribute "type". According to this blog post, the xsi:type attribute is special and can't be accessed by usal keywords/functions. How can I do it? PS: I tried with WITH XMLNAMESPACES ( 'http://www.educations.com/Search/Parameters.xsd' as p, 'http://www.w3.org/2001/XMLSchema-instance' as xsi ) SELECT @X.value('(/p:parameters/p:parameter/@xsi:type)[1]','nvarchar(max)') but it didn't work.

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  • SEO redirects for removed pages

    - by adam
    Hi, Apologies if SO is not the right place for this, but there are 700+ other SEO questions on here. I'm a senior developer for a travel site with 12k+ pages. We completely redeveloped the site and relaunched in January, and with the volatile nature of travel, there are many pages which are no longer on the site. Examples: /destinations/africa/senegal.aspx /destinations/africa/features.aspx Of course, we have a 404 page in place (and it's a hard 404 page rather than a 30x redirect to a 404). Our SEO advisor has asked us to 30x redirect all our 404 pages (as found in Webmaster Tools), his argument being that 404's are damaging to our pagerank. He'd want us to redirect our Senegal and features pages above to the Africa page (which doesn't contain the content previously found on Senegal.aspx or features.aspx). An equivalent for SO would be taking a url for a removed question and redirecting it to /questions rather than showing a 404 'Question/Page not found'. My argument is that, as these pages are no longer on the site, 404 is the correct status to return. I'd also argue that redirecting these to less relevant pages could damage our SEO (due to duplicate content perhaps)? It's also very time consuming redirecting all 404's when our site takes some content from our in-house system, which adds/removes content at will. Thanks for any advice, Adam

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  • SQL SERVER Mirroring Configured Without Domain The server network address TCP://SQLServerName:5023

    Regular readers of my blog will be aware of my friend who called me few days ago with very a funny SQL Problem SQL SERVER SSMS Query Command(s) completed successfully without ANY Results. This time, it did not take long before he called me up with another interesting problem, although the issue he was [...]...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Ubuntu Server Cannot Route to the Internet

    - by ejes
    I've been having this problem for weeks now, and I can't seem to figure out the problem. My server can route the local network and serves it well, however it cannot access the internet. It can't be the router because everything else on this lan can route through the router. I've even switched the ethernet port. Any help would be appreciated. I've tried all the usual places, anyway, here are the configs: root@uhs:~# uname -a Linux uhs 3.0.0-16-generic-pae #28-Ubuntu SMP Fri Jan 27 19:24:01 UTC 2012 i686 i686 i386 GNU/Linux root@uhs:~# cat /etc/network/interfaces # This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). # The loopback network interface auto lo iface lo inet loopback # The primary network interface # auto eth1 # iface eth1 inet dhcp auto eth0 iface eth0 inet static address 192.168.0.3 netmask 255.255.255.0 broadcast 192.168.0.255 gateway 192.168.0.1 root@uhs:~# ping -c 4 192.168.0.1 PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data. 64 bytes from 192.168.0.1: icmp_req=1 ttl=64 time=0.334 ms 64 bytes from 192.168.0.1: icmp_req=2 ttl=64 time=0.339 ms 64 bytes from 192.168.0.1: icmp_req=3 ttl=64 time=0.324 ms 64 bytes from 192.168.0.1: icmp_req=4 ttl=64 time=0.339 ms --- 192.168.0.1 ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 2997ms rtt min/avg/max/mdev = 0.324/0.334/0.339/0.006 ms root@uhs:~# ping -c 4 209.85.145.103 PING 209.85.145.103 (209.85.145.103) 56(84) bytes of data. --- 209.85.145.103 ping statistics --- 4 packets transmitted, 0 received, 100% packet loss, time 3023ms root@uhs:~# ifconfig eth0 Link encap:Ethernet HWaddr 00:0c:6e:a0:92:6e inet addr:192.168.0.3 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::20c:6eff:fea0:926e/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:13131114 errors:0 dropped:0 overruns:0 frame:0 TX packets:10540297 errors:0 dropped:0 overruns:5 carrier:0 collisions:0 txqueuelen:1000 RX bytes:3077922794 (3.0 GB) TX bytes:3827489734 (3.8 GB) Interrupt:10 Base address:0xa000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:7721 errors:0 dropped:0 overruns:0 frame:0 TX packets:7721 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:551950 (551.9 KB) TX bytes:551950 (551.9 KB) root@uhs:~# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.0.1 0.0.0.0 UG 100 0 0 eth0 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 root@uhs:~# # PRETEND Traceroute root@uhs:~# for i in {1..30}; do ping -t $i -c 1 209.85.145.103; done | grep "Time to live exceeded" root@uhs:~#

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  • new ubuntu server installation - java server not receiving packets

    - by James
    I have developed a Java server which listens for UDP packets which come from mobile devices. At the moment, it works correctly if I run my Server on my windows PC. I can receive and respond to the UDP packets sent from my phone (over 3g, not wifi). However, I am trying to run the Server on a different computer which I found lying around my house. I have basically done a clean install of Ubuntu Server edition, updated it, installed the java run time environment and configured port forwarding to allow connections on the appropriate port. I have also tried to disable the firewall. The problem is, it doesn't appear as if the server is receiving any packets and I've exhausted my brain thinking on how to solve/debug the problem. Can anyone suggest to me what the problem might be? or more likely something I can do to help me find out more information about what is going wrong.

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  • Why does a Non-existant page returns 302 status when using a custom 404 page in asp.net

    - by webdevbytes
    I have setup custom 404 page custom404.aspx that returns a 404 Not Found error correctly, however the non-existant page that was initially requested returns a 302 Found status. So when I test thispagedoesnotexist.aspx, it returns a 302 Found then the custom404.aspx loads and returns a 404 Not Found status. I want to make sure that search spiders/bots understand that the requested page does not exist and should not show up in any search results. Is this the case? Cheers

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