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  • How to implement automatic reflection of direct SQL Updates of the underlying database, in an ActiveRecord in Ruby on Rails ?

    - by Vadim Eisenberg
    Hello ! I am new to Ruby on Rails and I have a (maybe naive) question: I want to implement reflection of direct SQL Updates of the underlying database in an ActiveRecord (and finally in the generated html). By "direct updates" I mean updating the database bypassing the ActiveRecord methods, for example by MySQL console. I guess here MySQL triggers could be used that would call some stored procedure that would cause the appropriate ActiveRecord to be reloaded. Is there some automatic handling of this scenario in ActiveRecord/Ruby on Rails ? Did somebody implement this scenario ? Can somebody recommend using other MVC frameworks to reflect direct changes in mapped databases ?

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  • if there is any technique to insert values into multiple tables in sql Server 2008 Database?

    - by Krishanu Dey
    I just wanted to know, if there is any technique to insert values into multiple tables in sql Server 2008 Database? I've got the following cmd.CommandText = "Insert into tb1 (col1, col2, col3) values (@col1, @col2, @col3); Insert into tb2 (col1, col2, col3) values (@col11, @col12, @col13);"; cmd.Parameters.AddWithValue("col1","val1"); cmd.Parameters.AddWithValue("col2", "val2"); cmd.Parameters.AddWithValue("col3", "val3"); cmd.Parameters.AddWithValue("col11","val4"); cmd.Parameters.AddWithValue("col12", "val5"); cmd.Parameters.AddWithValue("col13", "val6"); But will values be inserted to "tb1" even if "Insert into tb2..." part gets an error? if yes then it is not what i wanted. i wanted that, values should not be inserted into tb1 if tb2 part gets an error. please help me out.

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  • How to test if a string is inside a list of predinfined list of string in oracle pl/sql

    - by drupalspring
    I define a list a string which contains different country codes ( for example , USA ,CHINA ,HK ,JPN) How can I check that if a input variable equal to one of the country of the country list in pl/sql . I use the following code to test it but fail, how can I revise it? declare country_list CONSTANT VARCHAR2(200) := USA,CHINA,HK,JPN; input VARCHAR2(200); begin input := 'JPN'; IF input IN (country_list) DBMS_OUTPUT.PUT_LINE('It is Inside'); else DBMS_OUTPUT.PUT_LINE('It is not Inside'); END IF; end;

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  • Fastest way to store/retrieve a dictionary - SQL, text file...?

    - by AP257
    Hi all, This is a really really super dumb question, so I apologise, but I'd be grateful for some advice. I've got a text file of words and word frequencies. It's very large - theoretically we're talking millions of rows. I just want to retrieve values from the file, and do it as quickly and efficiently as possible (for a web app, in Django). My question is: what is the best way to store and retrieve the values? Should import them into SQL? Or keep the file and use grep? Or put them into a JSON dictionary...? Or some other way? Sorry for the dumb question, would be very grateful for advice!

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  • Drawing up a session value within SQL query? PHP and MySQL

    - by Derek
    Hi, on one of my web pages I want my manager user to view all activities assigned to them (personally). In order to do this, I need something like this: $sql = "SELECT * FROM activities WHERE manager = $_SESSION['SESS_FULLNAME']"; Now obviously this syntax is all wrong, but because I am new to this stuff, is there a way I can call up the full name from the user's session within a query? This is so that when I call up the database values to be displayed within the web page, only the activities for the manager who is logged in is displayed. For example, the activities table has a manager column of a full name entry. Any help is much appreciated. Thanks.

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  • does this raw sql only one trip to the database or many trips?

    - by Álvaro García
    I gues that I have this sql: string strTSQL = "Begin TRAN delete from MyTable where ID = 1"; string strTSQL = ";delete from MyTable where ID = 2"; string strTSQL = ";delete from MyTable where ID = 3 COMMIT"; using(Entities dbContext = new Entities()) { dbCntext.MyTable.SQLQuery(strTSQL); } This use a transaction in the dataBase, so all the commands are executed or no one. But how I execute it through EF, it does only one trip to the database or many? Thanks.

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  • Is there any difference between SQL running in code vs the MySQL command line?

    - by MJB
    I have a SQL update statement I am running from inside a PHP program. It is prepared and then executed. When I run it in PHP, it reports a constraint violation. When I run the exact same statement from the command line (which I am getting via dBug()), it works with no errors. This sounds impossible, so I keep looking for differences between the statements. The only thing I can see is that when I execute it with an array of arguments, they all appear to be chars, when some should be integers. Any suggestions for where to look? I can post the code, but that does not seem like it would be helpful, because the code works.

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  • Why does SQLite say it can't read SQL from a file?

    - by Gavin
    Hi all. I have a bunch of SQL in a file, which creates the tables and so forth. The problem is that the .read command simply returns "can't open xxx" when I try to execute it. I've set the permissions to everybody read/write, but that didn't help. I can cat the file from the command line and see it fine. This is under Mac OS 10.6.3. Anybody have any idea here? Thanks!

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  • Why is Zend Framework (Zend_Db_table) rejecting this SQL Query?

    - by Michael T. Smith
    I'm working on a simple JOIN of two tables (urls and companies). I am using this query call: print $this->_db->select()->from(array('u' => 'urls'), array('id', 'url', 'company_id')) ->join(array('c' => 'companies'), 'u.company_id = c.id'); which is out putting this query: SELECT `u`.`id`, `u`.`url`, `u`.`company_id`, `c`.* FROM `urls` AS `u` INNER JOIN `companies` AS `c` ON u.company_id = c.id Now, I'd prefer the c.* to not actually appear, but either way it doesn't matter. ZF dies with this error: SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1" but I can run that query perfectly fine in my MySQL CLI. Any ideas how to fix up this query?

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  • How to version SQL Server schema using VS 2005?

    - by Mike
    I am new to C# programming and am coming to it most recently from working with Ruby on Rails. In RoR, I am used to being able to write schema migrations for the database. I would like to be able to do something similar for my C#/SQLServer projects. Does such a tool exist for the VS 2005 toolset? Would it be wise to use RoR migrations with SQL Server directly outside of VS 2005? In other words, I would handle all schema versioning using ActiveRecord:Migration from Rails but nothing else. If I do handle migrations outside of C# and VS 2005 with another tool, is RoR ActiveRecord:Migration the best thing to use or is there something which is a better fit?

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  • You have an error in your SQL syntax; check the manual that corresponds to your MySQL

    - by LuisEValencia
    I am trying to run a mysql query to find all occurences of a text. I have a syntax error but dont know where or how to fix it I am using sqlyog to execute this script DECLARE @url VARCHAR(255) SET @url = '1720' SELECT 'select * from ' + RTRIM(tbl.name) + ' where ' + RTRIM(col.name) + ' like %' + RTRIM(@url) + '%' FROM sysobjects tbl INNER JOIN syscolumns col ON tbl.id = col.id AND col.xtype IN (167, 175, 231, 239) -- (n)char and (n)varchar, there may be others to include AND col.length > 30 -- arbitrary min length into which you might store a URL WHERE tbl.type = 'U' -- user defined table 1 queries executed, 0 success, 1 errors, 0 warnings Query: declare @url varchar(255) set @url = '1720' select 'select * from ' + rtrim(tbl.name) + ' where ' + rtrim(col.name) + ' like %' ... Error Code: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'declare @url varchar(255)

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  • Number 0 is not saving to database as a prefix in SQL Server of CHAR data type column

    - by gmhk
    I am trying to insert an value as '019393' into a table with a CHAR(10) column. It is inserting only '19393' into the database I am implementing this feature in a stored procedure, doing some manipulation like incrementing that number by 15 and saving it back with '0' as the prefix I am using SQL Server database Note: I tried CASTING that value as VARCHAR before saving to the database, but even that did not get the solution Code SELECT @fromBSB = fromBSB, @toBSB = toBSB, @type = Type FROM [dbo].[tbl_REF_SpecialBSBRanges] WHERE CAST(@inputFromBSB AS INT) BETWEEN fromBSB AND toBSB SET @RETURNVALUE = @fromBSB IF(@fromBSB = @inputFromBSB) BEGIN PRINT 'Starting Number is Equal'; DELETE FROM tbl_REF_SpecialBSBRanges WHERE Type = @type AND fromBSB = @fromBSB AND toBSB = @toBSB INSERT INTO [tbl_REF_SpecialBSBRanges] ([Type], [fromBSB], [toBSB]) VALUES(@type, CAST('0' + @fromBSB + 1 AS CHAR), @toBSB) INSERT INTO [tbl_REF_SpecialBSBRanges] ([Type], [fromBSB], [toBSB]) VALUES(@inputBSBName, @inputFromBSB, @inputToBSB) END

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  • Quiz module as a part of SQL Tutorial (Project) in C#. Help!

    - by N1107
    Kindly help. Am a beginner in C#. The details of my project work include: Front End: C# Back End: SQL MS Visual Studio 2010 Windows Application Quiz Module Each session contains 20 questions. At the end of the test, the test-engine will evaluate the answers. If the student obtains more than 50% then he can unlock the next module. And his test score is printed using Crystal Reports and saved in teacher's database, against that student's record. Else, if his score is less than 50%, the test-engine will count the no. of attempts to clear the quiz & randomly generate another set of 20 questions from a file (from the teacher's database). It's complicated for me cause am a beginner. Would appreciate some help. Thanks.

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  • TDD vs. Unit testing

    - by Walter
    My company is fairly new to unit testing our code. I've been reading about TDD and unit testing for some time and am convinced of their value. I've attempted to convince our team that TDD is worth the effort of learning and changing our mindsets on how we program but it is a struggle. Which brings me to my question(s). There are many in the TDD community who are very religious about writing the test and then the code (and I'm with them), but for a team that is struggling with TDD does a compromise still bring added benefits? I can probably succeed in getting the team to write unit tests once the code is written (perhaps as a requirement for checking in code) and my assumption is that there is still value in writing those unit tests. What's the best way to bring a struggling team into TDD? And failing that is it still worth writing unit tests even if it is after the code is written? EDIT What I've taken away from this is that it is important for us to start unit testing, somewhere in the coding process. For those in the team who pickup the concept, start to move more towards TDD and testing first. Thanks for everyone's input. FOLLOW UP We recently started a new small project and a small portion of the team used TDD, the rest wrote unit tests after the code. After we wrapped up the coding portion of the project, those writing unit tests after the code were surprised to see the TDD coders already done and with more solid code. It was a good way to win over the skeptics. We still have a lot of growing pains ahead, but the battle of wills appears to be over. Thanks for everyone who offered advice!

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  • WPF - DataTemplate to show only one hierarchical level in recursive data

    - by Paull
    Hi all, I am using a tree to display my data: persons grouped by their teams. In my model a team can contain another team, so the recursion. I want do display details about the selected node of the tree using a contentpresenter. If the selection is a person, everything is fine: I can show the person name or datails without problem using a simple datatemplate. If the selection is a team I would like to display the team name followed by a list of member names. If one of these members is another team I would like to display just the team name, without recursion... My code here is wrong because it displays data in a recursive way, what is the right way of doing it? Thanks in advance for any help! best regards, Paolo <ContentPresenter Content="{Binding Path=SelectedItem, ElementName=PeopleTree}" > <ContentPresenter.Resources> <DataTemplate DataType="{x:Type my:PersonViewModel}"> <TextBlock Text="{Binding PersonName}"/> </DataTemplate> <DataTemplate DataType="{x:Type my:TeamViewModel}"> <StackPanel> <TextBlock Text="{Binding TeamName}" /> <ListBox ItemsSource="{Binding Members}" /> </StackPanel> </DataTemplate> </ContentPresenter.Resources> </ContentPresenter>

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  • rails2 and aws-simple (simpledb): data cannot be deleted from amazon simpledb?

    - by z3cko
    i am developing a ruby on rails (2.3.8) application with data storage amazon simpledb. i am using the aws-sdb gem in the version aws-sdb (0.3.1) there are a few bugs, but the problems are outlined in the comments of this tutorial from amazon: http://developer.amazonwebservices.com/connect/entry.jspa?externalID=1242 i am wondering if it is a bug of the gem or maybe a proxy issue, but i cannot delete any data from simpledb. anyone else experienced this or has a clue? >> t=Team.find(:first) => #<Team:0x329f718 @prefix_options={}, @attributes={"updated_at"=>Fri May 28 16:33:17 UTC 2010, "id"=>0}> >> t.destroy => #<Net::HTTPOK 200 OK readbody=true> >> t=Team.find(:first) => #<Team:0x321ad38 @prefix_options={}, @attributes={"updated_at"=>Fri May 28 16:33:17 UTC 2010, "id"=>0}> the team model is a normal ActiveResource Model, according to said tutorial. class Team < ActiveResource::Base self.site = "http://localhost:8888" # Proxy host + port self.prefix = "/fb2010_dev/" # SDB domain end

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  • What is Linq?

    - by Aamir Hasan
    The way data can be retrieved in .NET. LINQ provides a uniform way to retrieve data from any object that implements the IEnumerable<T> interface. With LINQ, arrays, collections, relational data, and XML are all potential data sources. Why LINQ?With LINQ, you can use the same syntax to retrieve data from any data source:var query = from e in employeeswhere e.id == 1select e.nameThe middle level represents the three main parts of the LINQ project: LINQ to Objects is an API that provides methods that represent a set of standard query operators (SQOs) to retrieve data from any object whose class implements the IEnumerable<T> interface. These queries are performed against in-memory data.LINQ to ADO.NET augments SQOs to work against relational data. It is composed of three parts.LINQ to SQL (formerly DLinq) is use to query relational databases such as Microsoft SQL Server. LINQ to DataSet supports queries by using ADO.NET data sets and data tables. LINQ to Entities is a Microsoft ORM solution, allowing developers to use Entities (an ADO.NET 3.0 feature) to declaratively specify the structure of business objects and use LINQ to query them. LINQ to XML (formerly XLinq) not only augments SQOs but also includes a host of XML-specific features for XML document creation and queries. What You Need to Use LINQLINQ is a combination of extensions to .NET languages and class libraries that support them. To use it, you’ll need the following: Obviously LINQ, which is available from the new Microsoft .NET Framework 3.5 that you can download at http://go.microsoft.com/?linkid=7755937.You can speed up your application development time with LINQ using Visual Studio 2008, which offers visual tools such as LINQ to SQL designer and the Intellisense  support with LINQ’s syntax.Optionally, you can download the Visual C# 2008 Expression Edition tool at www.microsoft.com/vstudio/express/download. It is the free edition of Visual Studio 2008 and offers a lot of LINQ support such as Intellisense and LINQ to SQL designer. To use LINQ to ADO.NET, you need SQL

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  • Change Data Capture Webinar

    I am going to be doing a webinar with our friends at Attunity on Change Data Capture.  Attunity have a good story around this technology and you can use it in your SSIS loads to great effect. Join Attunity and Konesans/SQLIS for a Webinar on 17 September Space is limited. Reserve your Webinar seat now at: https://www1.gotomeeting.com/register/693735512 Want increased efficiency and real-time speed when conducting ETL loads? Need lower implementation costs while minimizing system impact? Learn how change data capture (CDC) technologies can reduce ETL load times. Allan Mitchell, Principal Consultant at Konesans and SQLServer MVP specialising in ETL, will explain CDC concepts and benefits and how CDC can dramatically reduce ETL load times. Ian Archibald, Pre-Sales Director EMEA for Attunity, will present and demonstrate Attunity's award-winning Oracle-CDC for SSIS, a fully-integrated SSIS solution for designing, deploying and managing Oracle CDC processes. Title: Change Data Capture - Reducing ETL Load Times Date: Thursday, September 17, 2009 Time: 10:00 AM - 11:00 AM BST ABOUT THE SPEAKERS: Allan Mitchell is the joint owner of Konesans Ltd, a UK based consultancy specializing in SQL Server, and most importantly SQL Server Integration Services. Having been working with SQL Server from 6.5 onwards, he has extensive experience in many aspects of SQL Server, but now focuses on the BI suite of tools. He is a SQL Server MVP, a frequent poster on the MS SSIS/DTS newsgroups, and runs the sqldts.com and sqlis.com resource sites. Ian Archibald, Attunity Pre-Sales Director EMEA, has worked in Attunity’s UK Office for 17 years. An expert in Attunity solutions, Ian has extensive knowledge of Attunity’s products and data integration & CDC technologies. After registering you will receive a confirmation email containing information about joining the Webinar. System Requirements PC-based attendees Required: Windows® 2000, XP Home, XP Pro, 2003 Server, Vista Macintosh®-based attendees Required: Mac OS® X 10.4 (Tiger®) or newer

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  • Change Data Capture Webinar

    I am going to be doing a webinar with our friends at Attunity on Change Data Capture.  Attunity have a good story around this technology and you can use it in your SSIS loads to great effect. Join Attunity and Konesans/SQLIS for a Webinar on 17 September Space is limited. Reserve your Webinar seat now at: https://www1.gotomeeting.com/register/693735512 Want increased efficiency and real-time speed when conducting ETL loads? Need lower implementation costs while minimizing system impact? Learn how change data capture (CDC) technologies can reduce ETL load times. Allan Mitchell, Principal Consultant at Konesans and SQLServer MVP specialising in ETL, will explain CDC concepts and benefits and how CDC can dramatically reduce ETL load times. Ian Archibald, Pre-Sales Director EMEA for Attunity, will present and demonstrate Attunity's award-winning Oracle-CDC for SSIS, a fully-integrated SSIS solution for designing, deploying and managing Oracle CDC processes. Title: Change Data Capture - Reducing ETL Load Times Date: Thursday, September 17, 2009 Time: 10:00 AM - 11:00 AM BST ABOUT THE SPEAKERS: Allan Mitchell is the joint owner of Konesans Ltd, a UK based consultancy specializing in SQL Server, and most importantly SQL Server Integration Services. Having been working with SQL Server from 6.5 onwards, he has extensive experience in many aspects of SQL Server, but now focuses on the BI suite of tools. He is a SQL Server MVP, a frequent poster on the MS SSIS/DTS newsgroups, and runs the sqldts.com and sqlis.com resource sites. Ian Archibald, Attunity Pre-Sales Director EMEA, has worked in Attunity’s UK Office for 17 years. An expert in Attunity solutions, Ian has extensive knowledge of Attunity’s products and data integration & CDC technologies. After registering you will receive a confirmation email containing information about joining the Webinar. System Requirements PC-based attendees Required: Windows® 2000, XP Home, XP Pro, 2003 Server, Vista Macintosh®-based attendees Required: Mac OS® X 10.4 (Tiger®) or newer

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  • Uploading documents to WSS (Windows Sharepoint Services) using SSIS

    - by Randy Aldrich Paulo
    Recently I was tasked to create an SSIS application that will query a database, split the results with certain criteria and create CSV file for every result and upload the file to a Sharepoint Document Library site. I've search the web and compiled the steps I've taken to build the solution. Summary: A) Create a proxy class of WSS Copy.asmx. B) Create a wrapper class for the proxy class and add a mechanism to check if the file is existing and delete method. C) Create an SSIS and call the wrapper class to transfer the files.   A) Creating Proxy Class 1) Go to Visual Studio Command Prompt type wsdl http://[sharepoint site]/_vti_bin/Copy.asmx this will generate the proxy class (Copy.cs) that will be added to the solution. 2) Add Copy.cs to solution and create another constructor for Copy() that will accept additional parameters url, userName, password and domain.   public Copy(string url, string userName, string password, string domain) { this.Url = url; this.Credentials = new System.Net.NetworkCredential(userName, password, domain); } 3) Add a namespace.     B) Wrapper Class Create a C# new library that references the Proxy Class.         C) Create SSIS SSIS solution is composed of:   1) Execute SQL Task, returns a single column rows containing the criteria. 2) Foreach Loop Container - loops per result from query (SQL Task) and creates a CSV file on a certain folder. 3) Script Task - calls the wrapper class to upload CSV files located on a certain folder to targer WSS Document Library Note: I've created another overload of CopyFiles that accepts a Directory Info instead of file location that loops thru the contents of the folder. Designer View Variable View

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  • Logging connection strings

    If you some of the dynamic features of SSIS such as package configurations or property expressions then sometimes trying to work out were your connections are pointing can be a bit confusing. You will work out in the end but it can be useful to explicitly log this information so that when things go wrong you can just review the logs. You may wish to develop this idea further and encapsulate such logging into a custom task, but for now lets keep it simple and use the Script Task. The Script Task code below will raise an Information event showing the name and connection string for a connection. Imports System Imports Microsoft.SqlServer.Dts.Runtime Public Class ScriptMain Public Sub Main() Dim fireAgain As Boolean ' Get the connection string, we need to know the name of the connection Dim connectionName As String = "My OLE-DB Connection" Dim connectionString As String = Dts.Connections(connectionName).ConnectionString ' Format the message and log it via an information event Dim message As String = String.Format("Connection ""{0}"" has a connection string of ""{1}"".", _ connectionName, connectionString) Dts.Events.FireInformation(0, "Information", message, Nothing, 0, fireAgain) Dts.TaskResult = Dts.Results.Success End Sub End Class Building on that example it is probably more flexible to log all connections in a package as shown in the next example. Imports System Imports Microsoft.SqlServer.Dts.Runtime Public Class ScriptMain Public Sub Main() Dim fireAgain As Boolean ' Loop through all connections in the package For Each connection As ConnectionManager In Dts.Connections ' Get the connection string and log it via an information event Dim message As String = String.Format("Connection ""{0}"" has a connection string of ""{1}"".", _ connection.Name, connection.ConnectionString) Dts.Events.FireInformation(0, "Information", message, Nothing, 0, fireAgain) Next Dts.TaskResult = Dts.Results.Success End Sub End Class By using the Information event it makes it readily available in the designer, for example the Visual Studio Output window (Ctrl+Alt+O) or the package designer Execution Results tab, and also allows you to readily control the logging by choosing which events to log in the normal way. Now before somebody starts commenting that this is a security risk, I would like to highlight good practice for building connection managers. Firstly the Password property, or any other similar sensitive property is always defined as write-only, and secondly the connection string property only uses the public properties to assemble the connection string value when requested. In other words the connection string will never contain the password. I have seen a couple of cases where this is not true, but that was just bad development by third-parties, you won’t find anything like that in the box from Microsoft.   Whilst writing this code it made me wish that there was a custom log entry that you could just turn on that did this for you, but alas connection managers do not even seem to support custom events. It did however remind me of a very useful event that is often overlooked and fits rather well alongside connection string logging, the Execute SQL Task’s custom ExecuteSQLExecutingQuery event. To quote the help reference Custom Messages for Logging - Provides information about the execution phases of the SQL statement. Log entries are written when the task acquires connection to the database, when the task starts to prepare the SQL statement, and after the execution of the SQL statement is completed. The log entry for the prepare phase includes the SQL statement that the task uses. It is the last part that is so useful, how often have you used an expression to derive a SQL statement and you want to log that to make sure the correct SQL is being returned? You need to turn it one, by default no custom log events are captured, but I’ll refer you to a walkthrough on setting up the logging for ExecuteSQLExecutingQuery by Jamie.

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  • No mapping between account names and security IDs was done

    - by ybbest
    When I try to install SQL Server 2008 R2, I got the error “No mapping between account names and security IDs was done” when I try to set the SQL Server Database engine services identity to a domain user name. The reason I am getting the error is that I create a base VM forgot to run sysprep, before I copy the VM and used to install SQL servers. You need to run the sysprep as follows: References: How to Sysprep in Windows Server 2008 R2 and Windows 7

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  • So long and thanks for the fish&hellip;

    - by Geoff N. Hiten
    This marks my last post as a SQLPASS Board member.  I learned a lot during my year of service and I thank everyone involved for this opportunity.  I would especially like to thank the Chapter leaders and Regional Mentors for Virtual Chapters who (mostly) patiently taught me about Virtual Chapters.   I hope the changes I put in place will help strengthen and grow VCs and PASS going forward.  I would also like to thank every one who encouraged me to reach beyond my comfort zone and accept a leadership position within the PASS organization.  My overall principle was to be a good steward of the PASS community.  Could I have done more?  Always. Did I do enough?  I hope so.  But PASS is a volunteer organization and my time, like yours, is limited.  I have other obligations in life that supersede PASS.  Now I have more time for some of those.  I won’t be going away or leaving the SQL Community.  I will still contribute to the community and support PASS, just in a different role.  Time to let somebody else enjoy the hot seat for a while. Finally, everyone who voted (not just for me) deserves a thanks.  More voters and more engaged voters, strong candidates, and a vigorous debate were all I wanted out of declaring as a candidate last year. This year the SQL community got exactly that. Thank you..

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  • Entity Framework v1 &ndash; tips and Tricks Part 3

    - by Rohit Gupta
    General Tips on Entity Framework v1 & Linq to Entities: ToTraceString() If you need to know the underlying SQL that the EF generates for a Linq To Entities query, then use the ToTraceString() method of the ObjectQuery class. (or use LINQPAD) Note that you need to cast the LINQToEntities query to ObjectQuery before calling TotraceString() as follows: 1: string efSQL = ((ObjectQuery)from c in ctx.Contact 2: where c.Address.Any(a => a.CountryRegion == "US") 3: select c.ContactID).ToTraceString(); ================================================================================ MARS or MultipleActiveResultSet When you create a EDM Model (EDMX file) from the database using Visual Studio, it generates a connection string with the same name as the name of the EntityContainer in CSDL. In the ConnectionString so generated it sets the MultipleActiveResultSet attribute to true by default. So if you are running the following query then it streams multiple readers over the same connection: 1: using (BAEntities context = new BAEntities()) 2: { 3: var cons = 4: from con in context.Contacts 5: where con.FirstName == "Jose" 6: select con; 7: foreach (var c in cons) 8: { 9: if (c.AddDate < new System.DateTime(2007, 1, 1)) 10: { 11: c.Addresses.Load(); 12: } 13: } 14: } ================================================================================= Explicitly opening and closing EntityConnection When you call ToList() or foreach on a LINQToEntities query the EF automatically closes the connection after all the records from the query have been consumed. Thus if you need to run many LINQToEntities queries over the same connection then explicitly open and close the connection as follows: 1: using (BAEntities context = new BAEntities()) 2: { 3: context.Connection.Open(); 4: var cons = from con in context.Contacts where con.FirstName == "Jose" 5: select con; 6: var conList = cons.ToList(); 7: var allCustomers = from con in context.Contacts.OfType<Customer>() 8: select con; 9: var allcustList = allCustomers.ToList(); 10: context.Connection.Close(); 11: } ====================================================================== Dispose ObjectContext only if required After you retrieve entities using the ObjectContext and you are not explicitly disposing the ObjectContext then insure that your code does consume all the records from the LinqToEntities query by calling .ToList() or foreach statement, otherwise the the database connection will remain open and will be closed by the garbage collector when it gets to dispose the ObjectContext. Secondly if you are making updates to the entities retrieved using LinqToEntities then insure that you dont inadverdently dispose of the ObjectContext after the entities are retrieved and before calling .SaveChanges() since you need the SAME ObjectContext to keep track of changes made to the Entities (by using ObjectStateEntry objects). So if you do need to explicitly dispose of the ObjectContext do so only after calling SaveChanges() and only if you dont need to change track the entities retrieved any further. ======================================================================= SQL InjectionAttacks under control with EFv1 LinqToEntities and LinqToSQL queries are parameterized before they are sent to the DB hence they are not vulnerable to SQL Injection attacks. EntitySQL may be slightly vulnerable to attacks since it does not use parameterized queries. However since the EntitySQL demands that the query be valid Entity SQL syntax and valid native SQL syntax at the same time. So the only way one can do a SQLInjection Attack is by knowing the SSDL of the EDM Model and be able to write the correct EntitySQL (note one cannot append regular SQL since then the query wont be a valid EntitySQL syntax) and append it to a parameter. ====================================================================== Improving Performance You can convert the EntitySets and AssociationSets in a EDM Model into precompiled Views using the edmgen utility. for e.g. the Customer Entity can be converted into a precompiled view using edmgen and all LinqToEntities query against the contaxt.Customer EntitySet will use the precompiled View instead of the EntitySet itself (the same being true for relationships (EntityReference & EntityCollections of a Entity)). The advantage being that when using precompiled views the performance will be much better. The syntax for generating precompiled views for a existing EF project is : edmgen /mode:ViewGeneration /inssdl:BAModel.ssdl /incsdl:BAModel.csdl /inmsl:BAModel.msl /p:Chap14.csproj Note that this will only generate precompiled views for EntitySets and Associations and not for existing LinqToEntities queries in the project.(for that use CompiledQuery.Compile<>) Secondly if you have a LinqToEntities query that you need to run multiple times, then one should precompile the query using CompiledQuery.Compile method. The CompiledQuery.Compile<> method accepts a lamda expression as a parameter, which denotes the LinqToEntities query  that you need to precompile. The following is a example of a lamda that we can pass into the CompiledQuery.Compile() method 1: Expression<Func<BAEntities, string, IQueryable<Customer>>> expr = (BAEntities ctx1, string loc) => 2: from c in ctx1.Contacts.OfType<Customer>() 3: where c.Reservations.Any(r => r.Trip.Destination.DestinationName == loc) 4: select c; Then we call the Compile Query as follows: 1: var query = CompiledQuery.Compile<BAEntities, string, IQueryable<Customer>>(expr); 2:  3: using (BAEntities ctx = new BAEntities()) 4: { 5: var loc = "Malta"; 6: IQueryable<Customer> custs = query.Invoke(ctx, loc); 7: var custlist = custs.ToList(); 8: foreach (var item in custlist) 9: { 10: Console.WriteLine(item.FullName); 11: } 12: } Note that if you created a ObjectQuery or a Enitity SQL query instead of the LINQToEntities query, you dont need precompilation for e.g. 1: An Example of EntitySQL query : 2: string esql = "SELECT VALUE c from Contacts AS c where c is of(BAGA.Customer) and c.LastName = 'Gupta'"; 3: ObjectQuery<Customer> custs = CreateQuery<Customer>(esql); 1: An Example of ObjectQuery built using ObjectBuilder methods: 2: from c in Contacts.OfType<Customer>().Where("it.LastName == 'Gupta'") 3: select c This is since the Query plan is cached and thus the performance improves a bit, however since the ObjectQuery or EntitySQL query still needs to materialize the results into Entities hence it will take the same amount of performance hit as with LinqToEntities. However note that not ALL EntitySQL based or QueryBuilder based ObjectQuery plans are cached. So if you are in doubt always create a LinqToEntities compiled query and use that instead ============================================================ GetObjectStateEntry Versus GetObjectByKey We can get to the Entity being referenced by the ObjectStateEntry via its Entity property and there are helper methods in the ObjectStateManager (osm.TryGetObjectStateEntry) to get the ObjectStateEntry for a entity (for which we know the EntityKey). Similarly The ObjectContext has helper methods to get an Entity i.e. TryGetObjectByKey(). TryGetObjectByKey() uses GetObjectStateEntry method under the covers to find the object, however One important difference between these 2 methods is that TryGetObjectByKey queries the database if it is unable to find the object in the context, whereas TryGetObjectStateEntry only looks in the context for existing entries. It will not make a trip to the database ============================================================= POCO objects with EFv1: To create POCO objects that can be used with EFv1. We need to implement 3 key interfaces: IEntityWithKey IEntityWithRelationships IEntityWithChangeTracker Implementing IEntityWithKey is not mandatory, but if you dont then we need to explicitly provide values for the EntityKey for various functions (for e.g. the functions needed to implement IEntityWithChangeTracker and IEntityWithRelationships). Implementation of IEntityWithKey involves exposing a property named EntityKey which returns a EntityKey object. Implementation of IEntityWithChangeTracker involves implementing a method named SetChangeTracker since there can be multiple changetrackers (Object Contexts) existing in memory at the same time. 1: public void SetChangeTracker(IEntityChangeTracker changeTracker) 2: { 3: _changeTracker = changeTracker; 4: } Additionally each property in the POCO object needs to notify the changetracker (objContext) that it is updating itself by calling the EntityMemberChanged and EntityMemberChanging methods on the changeTracker. for e.g.: 1: public EntityKey EntityKey 2: { 3: get { return _entityKey; } 4: set 5: { 6: if (_changeTracker != null) 7: { 8: _changeTracker.EntityMemberChanging("EntityKey"); 9: _entityKey = value; 10: _changeTracker.EntityMemberChanged("EntityKey"); 11: } 12: else 13: _entityKey = value; 14: } 15: } 16: ===================== Custom Property ==================================== 17:  18: [EdmScalarPropertyAttribute(IsNullable = false)] 19: public System.DateTime OrderDate 20: { 21: get { return _orderDate; } 22: set 23: { 24: if (_changeTracker != null) 25: { 26: _changeTracker.EntityMemberChanging("OrderDate"); 27: _orderDate = value; 28: _changeTracker.EntityMemberChanged("OrderDate"); 29: } 30: else 31: _orderDate = value; 32: } 33: } Finally you also need to create the EntityState property as follows: 1: public EntityState EntityState 2: { 3: get { return _changeTracker.EntityState; } 4: } The IEntityWithRelationships involves creating a property that returns RelationshipManager object: 1: public RelationshipManager RelationshipManager 2: { 3: get 4: { 5: if (_relManager == null) 6: _relManager = RelationshipManager.Create(this); 7: return _relManager; 8: } 9: } ============================================================ Tip : ProviderManifestToken – change EDMX File to use SQL 2008 instead of SQL 2005 To use with SQL Server 2008, edit the EDMX file (the raw XML) changing the ProviderManifestToken in the SSDL attributes from "2005" to "2008" ============================================================= With EFv1 we cannot use Structs to replace a anonymous Type while doing projections in a LINQ to Entities query. While the same is supported with LINQToSQL, it is not with LinqToEntities. For e.g. the following is not supported with LinqToEntities since only parameterless constructors and initializers are supported in LINQ to Entities. (the same works with LINQToSQL) 1: public struct CompanyInfo 2: { 3: public int ID { get; set; } 4: public string Name { get; set; } 5: } 6: var companies = (from c in dc.Companies 7: where c.CompanyIcon == null 8: select new CompanyInfo { Name = c.CompanyName, ID = c.CompanyId }).ToList(); ;

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  • Information regarding Collection 6233 - Implementing and Maintaining Business Intelligence in Micros

    - by Testas
    At the London SQL Server User Group I was asked a number of questions regarding the release of Collection 6233 - Implementing and Maintaining Business Intelligence in Microsoft® SQL Server® 2008: Integration Services, Reporting Services and Analysis Services, which has been authored by myself. Particularly regarding the SSIS component of the collection. Elearning is an interactive training experience that enables you to learn at your own pace. With a variety of learning tools including demonstrations, animations as well as written materials and the addition of labs that enables you to reinforce your learning. Microsoft Elearning can provide a valuable learning tool when you may not have the time to take out of the office to attend a courseThis 24-hour collection provides you with the skills and knowledge required to implement and maintain business intelligence solutions on SQL Server 2008 and also helps students to prepare for Exam 70-448 and you can buy each part individually see: http://www.microsoft.com/learning/elearning/course/6233.mspx   However, you will create a simple data warehouse in this collection and use SSIS to create packages to populate the data warehouse with data, exploring key concepts and tools to faciliatate this. This was a decision thart I took when writing this course based on feedback from hundreds of students who attended Microsoft Official Courses on SSIS. They wanted a course that allowed them to use SSIS to work with a data warehouse. This collection will certainly enable you to explore the options available in SSIS to meet this requirement while at the same time meeting the certification requirements I hope this answers the questions regarding this collection and hope you enjoy this collection   Chris  

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