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  • sql server - select top and bottom rows

    - by Adrian Faciu
    Hi, I'm using Sql Server 2005 and i'm trying to achieve something like: In the same select statement i want to get the first x rows and the last x rows. SELECT TOP(5) BOTTOM(5) Of course 'bottom' does not exist so i need other solution. I believe there is an easy and elegant solution that i'm not getting. Doing the select again with Group By Desc is not an option. Thanks.

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  • Exchange-Server Query

    - by Rudi Kershaw
    First, a little background. I've recently been taken on as a web and software developer for a small company, who has no other in-house IT support. They've been asking my opinion on lots of IT subjects that are quite far out of my comfort zone. I'm definitely not a network admin. Their IT consultancy contractor is pushing them to upgrade their dedicated exchange server, even though it seems like the one they currently have has a lot of life left in it and is running problem free. They say it's "coming to the natural end of it's life". They want to install a monster with a Xeon E5-2420, 32GB RAM, 2x 1TB HDDs, Windows Server 2012 and Microsoft Exchange 2010. They want to charge a small fortune for it. Basically, this system seems massively over the top seeing as it won't be doing anything else other than running as an exchange server for a company with less than 25 email accounts. My employers also have a file server system in-house that hosts three web apps, an SQL server, their local domain, print server and shared folders. That machine is using the same specs as the proposed new one, and it is barely using any of it's potential. I asked if Microsoft Exchange 2010 could be installed on their file server, but they said that MS Exchange can't run on the same system as an SQL server because for some reason they will eat up each others resources (even though the SQL server isn't touching 1% of the current system's CPU or RAM). My question is really, are they trying to rip my employers off? Could MS Exchange be installed on their other server (on a virtual instance or not), or does the old one even need replacing at all? Going with their current suggestion will cost the company in excess of £6k, and it seems entirely unnecessary. I apologies, because I know this is probably a little thin on details, but if I carry on I could end up writing a massive essay that no-one will want to read. I've been doing my research, but I'm not knowledgeable enough make any hard decisions. Let me know if you need any more details. Thank you for any help you can offer. Further Details: The new exchange would need to support Outlook Web App, 25 users, a few public mailboxes, and email exchange with Blackberries.

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  • Printer redirection on server 2003

    - by user137841
    On windows server 2003 when one user connects to the server via RDP the default printer of the server for her profile does not change to the redirected printer of the session. This only happens with the one user all the other users default printers defaults to their session printer automatically. I tried the following solution but there was no \Terminal Server\Printer Redirection in gpedit.msc http://technet.microsoft.com/en-us/library/cc731963(v=ws.10).aspx Computer Configuration\Policies\Administrative Templates\Windows Components\Terminal Services\Terminal Server\Printer Redirection Is there a different place to check the Printer Redirection?

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  • How to Enable Full-Text Index on Sql Server 2008 Table

    - by michaeldelorenzo
    Not sure what's happening with this, but here's my question. I have a Sql Server 2008 database that I need to be able to do full-text indexing/searching but when I try to setup my indices on the table, I get the following: I've tried running this stored procedure on my database and it's successful: EXEC sp_fulltext_database @action = 'enable' But I still get the above window and my full-text searches don't return any results when they should. What am I missing?

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  • Combining multiple condition in single case statement in Sql Server

    - by swetha
    According to the following description i have to frame a case ...End statement in Sql server ,help me to frame a complex case..End statement to fulfil the following condition. if PAT_ENT.SCR_DT is not null and PAT_ENTRY.ELIGIBILITY is null then display display 'Favor' if PAT_ENT.SCR_DT is not null and PAT_ENTRY.EL is equal to No, display 'Error' if PAT_ENTRY.EL is Yes and DS.DES is equal to null or OFF, display 'Active' if DS.DES is equal to N, display 'Early Term' if DS.DES is equal to Y, display 'Complete' Thanks in advance.

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  • Installed Service Pack 3 for SQL Server 2005 but it does not show up when selecting @@version

    - by Blegger
    We installed Service Pack 3 for SQL Server 2005 Standard Edition (64-bit). In the Add or Remove Programs menu we have the following entries under Microsoft SQL Server 2005 (64-bit): Service Pack 3 for SQL Server Integration Services 64-bit) ENU (KB955706) Service Pack 3 for SQL Server Notification Services 2005 (64-bit) ENU (KB955706) Service Pack 3 for SQL Server Database Services 2005 (64-bit) ENU (KB955706) Service Pack 3 for SQL Server Tools and Workstation Components 2005 (64-bit) ENU (KB955706) But when I run the following query on the server: select @@version I get this result: Microsoft SQL Server 2005 - 9.00.4035.00 (X64) Nov 24 2008 16:17:31 Copyright (c) 1988-2005 Microsoft Corporation Standard Edition (64-bit) on Windows NT 5.2 (Build 3790: Service Pack 2) Why does it not display that it is running Service Pack 3?

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  • how to connect SQL Server cubes using dotnet(C#)

    - by prince23
    Hi. I am new to this cubes concept in SQL Server. I need to connect to cubes and query and get a result and display that result in grid view Any help would be great telling how to connect to a cube, articles on it, code any thing that can help me to achieve the result Thank you.

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  • Best index(es) to use for an OR Statement in SQL Server

    - by Chuck Haines
    I have a table which has a bunch of columns but the two relevant ones are: Due_Amount MONEY Bounced_Due_Amount MONEY I have a SQL query like the following SELECT * FROM table WHERE (Due_Amount 0 OR Bounced_Due_Amount 0) Would the best index to put on this table for SQL Server 2008 be an index which includes both columns in the index, or should I put an separate index on each column?

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  • SQL SERVER – PAGELATCH_DT, PAGELATCH_EX, PAGELATCH_KP, PAGELATCH_SH, PAGELATCH_UP – Wait Type – Day 12 of 28

    - by pinaldave
    This is another common wait type. However, I still frequently see people getting confused with PAGEIOLATCH_X and PAGELATCH_X wait types. Actually, there is a big difference between the two. PAGEIOLATCH is related to IO issues, while PAGELATCH is not related to IO issues but is oftentimes linked to a buffer issue. Before we delve deeper in this interesting topic, first let us understand what Latch is. Latches are internal SQL Server locks which can be described as very lightweight and short-term synchronization objects. Latches are not primarily to protect pages being read from disk into memory. It’s a synchronization object for any in-memory access to any portion of a log or data file.[Updated based on comment of Paul Randal] The difference between locks and latches is that locks seal all the involved resources throughout the duration of the transactions (and other processes will have no access to the object), whereas latches locks the resources during the time when the data is changed. This way, a latch is able to maintain the integrity of the data between storage engine and data cache. A latch is a short-living lock that is put on resources on buffer cache and in the physical disk when data is moved in either directions. As soon as the data is moved, the latch is released. Now, let us understand the wait stat type  related to latches. From Book On-Line: PAGELATCH_DT Occurs when a task is waiting on a latch for a buffer that is not in an I/O request. The latch request is in Destroy mode. PAGELATCH_EX Occurs when a task is waiting on a latch for a buffer that is not in an I/O request. The latch request is in Exclusive mode. PAGELATCH_KP Occurs when a task is waiting on a latch for a buffer that is not in an I/O request. The latch request is in Keep mode. PAGELATCH_SH Occurs when a task is waiting on a latch for a buffer that is not in an I/O request. The latch request is in Shared mode. PAGELATCH_UP Occurs when a task is waiting on a latch for a buffer that is not in an I/O request. The latch request is in Update mode. PAGELATCH_X Explanation: When there is a contention of access of the in-memory pages, this wait type shows up. It is quite possible that some of the pages in the memory are of very high demand. For the SQL Server to access them and put a latch on the pages, it will have to wait. This wait type is usually created at the same time. Additionally, it is commonly visible when the TempDB has higher contention as well. If there are indexes that are heavily used, contention can be created as well, leading to this wait type. Reducing PAGELATCH_X wait: The following counters are useful to understand the status of the PAGELATCH: Average Latch Wait Time (ms): The wait time for latch requests that have to wait. Latch Waits/sec: This is the number of latch requests that could not be granted immediately. Total Latch Wait Time (ms): This is the total latch wait time for latch requests in the last second. If there is TempDB contention, I suggest that you read the blog post of Robert Davis right away. He has written an excellent blog post regarding how to find out TempDB contention. The same blog post explains the terms in the allocation of GAM, SGAM and PFS. If there was a TempDB contention, Paul Randal explains the optimal settings for the TempDB in his misconceptions series. Trace Flag 1118 can be useful but use it very carefully. I totally understand that this blog post is not as clear as my other blog posts. I suggest if this wait stats is on one of your higher wait type. Do leave a comment or send me an email and I will get back to you with my solution for your situation. May the looking at all other wait stats and types together become effective as this wait type can help suggest proper bottleneck in your system. Read all the post in the Wait Types and Queue series. Note: The information presented here is from my experience and there is no way that I claim it to be accurate. I suggest reading Book OnLine for further clarification. All the discussions of Wait Stats in this blog are generic and vary from system to system. It is recommended that you test this on a development server before implementing it to a production server. Reference: Pinal Dave (http://blog.SQLAuthority.com)   Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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  • After restoring a SQL Server database from another server - get login fails

    - by Renso
    Issue: After you have restored a sql server database from another server, lets say from production to a Q/A environment, you get the "Login Fails" message for your service account. Reason: User logon information is stored in the syslogins table in the master database. By changing servers, or by altering this information by rebuilding or restoring an old version of the master database, the information may be different from when the user database dump was created. If logons do not exist for the users, they will receive an error indicating "Login failed" while attempting to log on to the server. If the user logons do exist, but the SUID values (for 6.x) or SID values (for 7.0) in master..syslogins and the sysusers table in the user database differ, the users may have different permissions than expected in the user database. Solution: Links a user entry in the sys.database_principals system catalog view in the current database to a SQL Server login of the same name. If a login with the same name does not exist, one will be created. Examine the result from the Auto_Fix statement to confirm that the correct link is in fact made. Avoid using Auto_Fix in security-sensitive situations. When you use Auto_Fix, you must specify user and password if the login does not already exist, otherwise you must specify user but password will be ignored. login must be NULL. user must be a valid user in the current database. The login cannot have another user mapped to it. execute the following stored procedure, in this example the login user name is "MyUser" exec sp_change_users_login 'Auto_Fix', 'MyUser'   NOTE: sp_change_users_login cannot be used with a SQL Server login created from a Windows principal or with a user created by using CREATE USER WITHOUT LOGIN.

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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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  • BizTalk 2009 - Installing BizTalk Server 2009 on XP for Development

    - by StuartBrierley
    At my previous employer, when developing for BizTalk Server 2004 using Visual Studio 2003, we made use of separate development and deployment environments; developing in Visual Studio on our client PCs and then deploying to a seperate shared BizTalk 2004 Server from there.  This server was part of a multi-server Standard BizTalk environment comprising of separate BizTalk Server 2004 and SQL Server 2000 servers.  This environment was implemented a number of years ago by an outside consulting company, and while it worked it did occasionally cause contention issues with three developers deploying to the same server to carry out unit testing! Now that I am making the design and implementation decisions about the environment that BizTalk will be developed in and deployed to, I have chosen to create a single "server" installation on my development PC, installling SQL Server 2008, Visual Studio 2008 and BizTalk Server 2009 on a single system.  The client PC in use is actually a MacBook Pro running Windows XP; not the most powerful of systems for high volume processing but it should be powerful enough to allow development and initial unit testing to take place. I did not need to, and so chose not to, install all of the components detailed in the Microsoft guide for installing BizTalk 2009 on Windows XP but I did follow the basics of the procedures detailed within.  Outlined below are the highlights of this process and any details of what choices I made.   Install IIS I had previsouly installed Windows XP, including all current service packs and critical updates.  At the time of installation this included Service Pack 3, the .Net Framework 3.5 and MS Windows Installer 3.1.  Having a running XP system, my first step was to install IIS - this is quite straightforward and posed no difficulties. Install Visual Studio 2008 The next step for me was to install Visual Studio 2008.  Making sure to select a custom installation is crucial at this point, as you need to make sure that you deselect SQL Server 2005 Express Edition as it can cause the BizTalk installation to fail.  The installation guide suggests that you only select Visual C# when selecting features to install, but  I decided that due to some legacy systems I have code for that I would also select the VB and ASP options. Visual Studio 2008 Service Pack 1 Following the completion of the installation of Visual Studio itself you should then install the Visual Studio 2008 Service Pack 1. SQL Server 2008 Standard Edition The next step before intalling BizTalk Server 2009 itself is to install SQL Server 2008 Standard Edition. On the feature selection screen make sure that you select the follwoing options: Database Engine Services SQL Server Replication Full-Text Search Analysis Services Reporting Services Business Intelligence Development Studio Client Tools Connectivity Integration Services Management Tools Basic and Complete Use the default instance and the same accounts for all SQL server instances - in my case I used the Network Service and Local Service accounts for the two sets of accounts. On the database engine configuration screen I selected windows authentication and added the current user, adding the same user again on the Analysis services Configuration screen.  All other screens were left on the default settings. The SQL Server 2008 installation also included the installation of hotfix for XP KB942288-v3, the Windows Installer 4.5 Redistributable. System Configuration At this stage I took a moment to disable the SQL Server shared memory protocol and enable the Named Pipes and TCP/IP protocols.  These can be found in the SQL Server Configuration Manager > SQL Server Network Configuration > Protocols for MSSQLServer.  I also made sure that the DTC settings were configured correctley.   BizTalk Server 2009 The penultimate step is to install BizTalk Server 2009 Standard Edition. I had previsouly downloaded the redistributable prerequisites as a CAB file so was able to make use of this when carrying out the installation. When selecting which components to install I selected: Server Runtime BizTalk EDI/AS2 Runtime WCF Adapter Runtime Portal Components Administrative Tools WFC Administartion Tools Developer Tools and SDK, Enterprise SSO Administration Module Enterprise SSO Master Secret Server Business Rules Components BAM Alert Provider BAM Client BAM Eventing Once installation has completed clear the launch BizTalk Server Configuration check box and select finish. Verify the Installation Before configuring BizTalk Server it is a good idea to check that BizTalk Server 2009 is installed and that SQL Server 2008 has started correctly.  The easiest way to verify the BizTalk installation is check the Programs and Features in Control panel.  Check that SQL is started by looking in the SQL Server Configuration Manager. Configure BizTalk Server 2009 Finally we are ready to configure BizTalk Server 2009.  To start this I opted for a custom configuration that allowed me to choose in more detail the settings to be used. For all databases I selected the local server and default database names. For all Accounts I used a local account that had been created specifically for the BizTalk Services. For all windows groups I allowed the configuration wizard to create the default local groups. The configuration wizard then ran:   Upon completion you will be presented with a screen detailing the success or failure of the configuration.  If your configuration failed you will need to sort out the issues and try again (it is possible to save the configuration settings for later use if you want too - except passwords of course!).  If you see lots of nice green ticks - congratulations BizTalk Server 2009 on XP is now installed and configured ready for development.

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  • SQL SERVER – Not Possible – Delete From Multiple Table – Update Multiple Table in Single Statement

    - by pinaldave
    There are two questions which I get every single day multiple times. In my gmail, I have created standard canned reply for them. Let us see the questions here. I want to delete from multiple table in a single statement how will I do it? I want to update multiple table in a single statement how will I do it? The answer is – No, You cannot and you should not. SQL Server does not support deleting or updating from two tables in a single update. If you want to delete or update two different tables – you may want to write two different delete or update statements for it. This method has many issues – from the consistency of the data to SQL syntax. Now here is the real reason for this blog post – yesterday I was asked this question again and I replied my canned answer saying it is not possible and it should not be any way implemented that day. In the response to my reply I was pointed out to my own blog post where user suggested that I had previously mentioned this is possible and with demo example. Let us go over my conversation – you may find it interesting. Let us call the user DJ. DJ: Pinal, can we delete multiple table in a single statement or with single delete statement? Pinal: No, you cannot and you should not. DJ: Oh okey, if that is the case, why do you suggest to do that? Pinal: (baffled) I am not suggesting that. I am rather suggesting that it is not possible and it should not be possible. DJ: Hmm… but in that case why did you blog about it earlier? Pinal: (What?) No, I did not. I am pretty confident. DJ: Well, I am confident as well. You did. Pinal: In that case, it is my word against your word. Isn’t it? DJ: I have proof. Do you want to see it that you suggest it is possible? Pinal: Yes, I will be delighted too. (After 10 Minutes) DJ: Here are not one but two of your blog posts which talks about it - SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – Part 1 of 2 SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – T-SQL Example – Part 2 of 2 Pinal: Oh! DJ: I know I was correct. Pinal: Well, oh man, I did not mean there what you mean here. DJ: I did not understand can you explain it further. Pinal: Here we go. The example in the other blog is the example of the cascading delete or cascading update. I think you may want to understand the concept of the foreign keys and cascading update/delete. The concept of cascading exists to maintain data integrity. If there primary keys get deleted the update or delete reflects on the foreign key table to maintain the key integrity and data consistency. SQL Server follows ANSI Entry SQL with regard to referential integrity between PrimaryKey and ForeignKey columns which requires the inserting, updating, and deleting of data in related tables to be restricted to values that preserve the integrity. This is all together different concept than deleting multiple values in a single statement. When I hear that someone wants to delete or update multiple table in a single statement what I assume is something very similar to following. DELETE/UPDATE Table 1 (cols) Table 2 (cols) VALUES … which is not valid statement/syntax as well it is not ASNI standards as well. I guess, after this discussion with DJ, I realize I need to do a blog post so I can add the link to this blog post in my canned answer. Well, it was a fun conversation with DJ and I hope it the message is very clear now. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Joins, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Weekly Series – Memory Lane – #004

    - by pinaldave
    Here is the list of curetted articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2006 Auto Generate Script to Delete Deprecated Fields in Current Database In early career everytime I have to drop a column, I had hard time doing it because I was scared what if that column was needed somewhere in the code. Due to this fear I never dropped any column. I just renamed the column. If the column which I renamed was needed afterwards it was very easy to rename it back again. However, it is not recommended to keep the deleted column renamed in the database. At every interval I used to drop the columns which was prefixed with specific word. This script is 6 years old but still works. Give it a look, I am open for improvements. 2007 Shrinking Truncate Log File – Log Full – Part 2 Shrinking database or mdf file is indeed bad thing and it creates lots of problems. However, once in a while there is legit requirement to shrink the log file – a very rare one. In the rare occasion shrinking or truncating the log file may be the only solution. However, one should make sure to take backup before and after the truncate or shrink as in case of a disaster they can be very useful. Remember that truncating log file will break the log chain and while restore it can create major issue. Anyway, use this feature with caution. 2008 Simple Use of Cursor to Print All Stored Procedures of Database Including Schema This is a very interesting requirement I used to face in my early career days, I needed to print all the Stored procedures of my database. Interesting enough I had written a cursor to do so. Today when I look back at this stored procedure, I believe there will be a much cleaner way to do the same task, however, I still use this SP quite often when I have to document all the stored procedures of my database. Interesting Observation about Order of Resultset without ORDER BY In industry many developers avoid using ORDER BY clause to display the result in particular order thinking that Index is enforcing the order. In this interesting example, I demonstrate that without using ORDER BY, same table and similar query can return different results. Query optimizer always returns results using any method which is optimized for performance. The learning is There is no order unless ORDER BY is used. 2009 Size of Index Table – A Puzzle to Find Index Size for Each Index on Table I asked this puzzle earlier where I asked how to find the Index size for each of the tables. The puzzle was very well received and lots of interesting answers were received. To answer this question I have written following blog posts. I suggest this weekend you try to solve this problem and see if you can come up with a better solution. If not, well here are the solutions. Solution 1 | Solution 2 | Solution 3 Understanding Table Hints with Examples Hints are options and strong suggestions specified for enforcement by the SQL Server query processor on DML statements. The hints override any execution plan the query optimizer might select for a query. The SQL Server Query optimizer is a very smart tool and it makes a better selection of execution plan. Suggesting hints to the Query Optimizer should be attempted when absolutely necessary and by experienced developers who know exactly what they are doing (or in development as a way to experiment and learn). Interesting Observation – TOP 100 PERCENT and ORDER BY I have seen developers and DBAs using TOP very causally when they have to use the ORDER BY clause. Theoretically, there is no need of ORDER BY in the view at all. All the ordering should be done outside the view and view should just have the SELECT statement in it. It was quite common that to save this extra typing by including ordering inside of the view. At several instances developers want a complete resultset and for the same they include TOP 100 PERCENT along with ORDER BY, assuming that this will simulate the SELECT statement with ORDER BY. 2010 SQLPASS Nov 8-11, 2010-Seattle – An Alternative Look at Experience In year 2010 I attended most prestigious SQL Server event SQLPASS between Nov 8-11, 2010 at Seattle. I have only one expression for the event - Best Summit Ever. Instead of writing about my usual routine or the event, I wrote about the interesting things I did and how I felt about it! When I go back and read it, I feel that this is the best event I attended in year 2010. Change Database Access to Single User Mode Using SSMS Image says all. 2011 SQL Server 2012 has introduced new analytic functions. These functions were long awaited and I am glad that they are now here. Before when any of this function was needed, people used to write long T-SQL code to simulate these functions. But now there’s no need of doing so. Having available native function also helps performance as well readability. Function SQLAuthority MSDN CUME_DIST CUME_DIST CUME_DIST FIRST_VALUE FIRST_VALUE FIRST_VALUE LAST_VALUE LAST_VALUE LAST_VALUE LEAD LEAD LEAD LAG LAG LAG PERCENTILE_CONT PERCENTILE_CONT PERCENTILE_CONT PERCENTILE_DISC PERCENTILE_DISC PERCENTILE_DISC PERCENT_RANK PERCENT_RANK PERCENT_RANK Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Diving into OpenStack Network Architecture - Part 1

    - by Ronen Kofman
    v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} rkofman Normal rkofman 83 3045 2014-05-23T21:11:00Z 2014-05-27T06:58:00Z 3 1883 10739 Oracle Corporation 89 25 12597 12.00 140 Clean Clean false false false false EN-US X-NONE HE MicrosoftInternetExplorer4 /* 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:Arial; mso-bidi-theme-font:minor-bidi; mso-bidi-language:AR-SA;} Before we begin OpenStack networking has very powerful capabilities but at the same time it is quite complicated. In this blog series we will review an existing OpenStack setup using the Oracle OpenStack Tech Preview and explain the different network components through use cases and examples. The goal is to show how the different pieces come together and provide a bigger picture view of the network architecture in OpenStack. This can be very helpful to users making their first steps in OpenStack or anyone wishes to understand how networking works in this environment.  We will go through the basics first and build the examples as we go. According to the recent Icehouse user survey and the one before it, Neutron with Open vSwitch plug-in is the most widely used network setup both in production and in POCs (in terms of number of customers) and so in this blog series we will analyze this specific OpenStack networking setup. As we know there are many options to setup OpenStack networking and while Neturon + Open vSwitch is the most popular setup there is no claim that it is either best or the most efficient option. Neutron + Open vSwitch is an example, one which provides a good starting point for anyone interested in understanding OpenStack networking. Even if you are using different kind of network setup such as different Neutron plug-in or even not using Neutron at all this will still be a good starting point to understand the network architecture in OpenStack. The setup we are using for the examples is the one used in the Oracle OpenStack Tech Preview. Installing it is simple and it would be helpful to have it as reference. In this setup we use eth2 on all servers for VM network, all VM traffic will be flowing through this interface.The Oracle OpenStack Tech Preview is using VLANs for L2 isolation to provide tenant and network isolation. The following diagram shows how we have configured our deployment: This first post is a bit long and will focus on some basic concepts in OpenStack networking. The components we will be discussing are Open vSwitch, network namespaces, Linux bridge and veth pairs. Note that this is not meant to be a comprehensive review of these components, it is meant to describe the component as much as needed to understand OpenStack network architecture. All the components described here can be further explored using other resources. Open vSwitch (OVS) In the Oracle OpenStack Tech Preview OVS is used to connect virtual machines to the physical port (in our case eth2) as shown in the deployment diagram. OVS contains bridges and ports, the OVS bridges are different from the Linux bridge (controlled by the brctl command) which are also used in this setup. To get started let’s view the OVS structure, use the following command: # ovs-vsctl show 7ec51567-ab42-49e8-906d-b854309c9edf     Bridge br-int         Port br-int             Interface br-int type: internal         Port "int-br-eth2"             Interface "int-br-eth2"     Bridge "br-eth2"         Port "br-eth2"             Interface "br-eth2" type: internal         Port "eth2"             Interface "eth2"         Port "phy-br-eth2"             Interface "phy-br-eth2" ovs_version: "1.11.0" We see a standard post deployment OVS on a compute node with two bridges and several ports hanging off of each of them. The example above is a compute node without any VMs, we can see that the physical port eth2 is connected to a bridge called “br-eth2”. We also see two ports "int-br-eth2" and "phy-br-eth2" which are actually a veth pair and form virtual wire between the two bridges, veth pairs are discussed later in this post. When a virtual machine is created a port is created on one the br-int bridge and this port is eventually connected to the virtual machine (we will discuss the exact connectivity later in the series). Here is how OVS looks after a VM was launched: # ovs-vsctl show efd98c87-dc62-422d-8f73-a68c2a14e73d     Bridge br-int         Port "int-br-eth2"             Interface "int-br-eth2"         Port br-int             Interface br-int type: internal         Port "qvocb64ea96-9f" tag: 1             Interface "qvocb64ea96-9f"     Bridge "br-eth2"         Port "phy-br-eth2"             Interface "phy-br-eth2"         Port "br-eth2"             Interface "br-eth2" type: internal         Port "eth2"             Interface "eth2" ovs_version: "1.11.0" Bridge "br-int" now has a new port "qvocb64ea96-9f" which connects to the VM and tagged with VLAN 1. Every VM which will be launched will add a port on the “br-int” bridge for every network interface the VM has. Another useful command on OVS is dump-flows for example: # ovs-ofctl dump-flows br-int NXST_FLOW reply (xid=0x4): cookie=0x0, duration=735.544s, table=0, n_packets=70, n_bytes=9976, idle_age=17, priority=3,in_port=1,dl_vlan=1000 actions=mod_vlan_vid:1,NORMAL cookie=0x0, duration=76679.786s, table=0, n_packets=0, n_bytes=0, idle_age=65534, hard_age=65534, priority=2,in_port=1 actions=drop cookie=0x0, duration=76681.36s, table=0, n_packets=68, n_bytes=7950, idle_age=17, hard_age=65534, priority=1 actions=NORMAL As we see the port which is connected to the VM has the VLAN tag 1. However the port on the VM network (eth2) will be using tag 1000. OVS is modifying the vlan as the packet flow from the VM to the physical interface. In OpenStack the Open vSwitch agent takes care of programming the flows in Open vSwitch so the users do not have to deal with this at all. If you wish to learn more about how to program the Open vSwitch you can read more about it at http://openvswitch.org looking at the documentation describing the ovs-ofctl command. Network Namespaces (netns) Network namespaces is a very cool Linux feature can be used for many purposes and is heavily used in OpenStack networking. Network namespaces are isolated containers which can hold a network configuration and is not seen from outside of the namespace. A network namespace can be used to encapsulate specific network functionality or provide a network service in isolation as well as simply help to organize a complicated network setup. Using the Oracle OpenStack Tech Preview we are using the latest Unbreakable Enterprise Kernel R3 (UEK3), this kernel provides a complete support for netns. Let's see how namespaces work through couple of examples to control network namespaces we use the ip netns command: Defining a new namespace: # ip netns add my-ns # ip netns list my-ns As mentioned the namespace is an isolated container, we can perform all the normal actions in the namespace context using the exec command for example running the ifconfig command: # ip netns exec my-ns ifconfig -a lo        Link encap:Local Loopback           LOOPBACK  MTU:16436 Metric:1           RX packets:0 errors:0 dropped:0 overruns:0 frame:0           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0           RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b) We can run every command in the namespace context, this is especially useful for debug using tcpdump command, we can ping or ssh or define iptables all within the namespace. Connecting the namespace to the outside world: There are various ways to connect into a namespaces and between namespaces we will focus on how this is done in OpenStack. OpenStack uses a combination of Open vSwitch and network namespaces. OVS defines the interfaces and then we can add those interfaces to namespace. So first let's add a bridge to OVS: # ovs-vsctl add-br my-bridge Now let's add a port on the OVS and make it internal: # ovs-vsctl add-port my-bridge my-port # ovs-vsctl set Interface my-port type=internal And let's connect it into the namespace: # ip link set my-port netns my-ns Looking inside the namespace: # ip netns exec my-ns ifconfig -a lo        Link encap:Local Loopback           LOOPBACK  MTU:65536 Metric:1           RX packets:0 errors:0 dropped:0 overruns:0 frame:0           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0           RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b) my-port   Link encap:Ethernet HWaddr 22:04:45:E2:85:21           BROADCAST  MTU:1500 Metric:1           RX packets:0 errors:0 dropped:0 overruns:0 frame:0           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0           RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b) Now we can add more ports to the OVS bridge and connect it to other namespaces or other device like physical interfaces. Neutron is using network namespaces to implement network services such as DCHP, routing, gateway, firewall, load balance and more. In the next post we will go into this in further details. Linux Bridge and veth pairs Linux bridge is used to connect the port from OVS to the VM. Every port goes from the OVS bridge to a Linux bridge and from there to the VM. The reason for using regular Linux bridges is for security groups’ enforcement. Security groups are implemented using iptables and iptables can only be applied to Linux bridges and not to OVS bridges. Veth pairs are used extensively throughout the network setup in OpenStack and are also a good tool to debug a network problem. Veth pairs are simply a virtual wire and so veths always come in pairs. Typically one side of the veth pair will connect to a bridge and the other side to another bridge or simply left as a usable interface. In this example we will create some veth pairs, connect them to bridges and test connectivity. This example is using regular Linux server and not an OpenStack node: Creating a veth pair, note that we define names for both ends: # ip link add veth0 type veth peer name veth1 # ifconfig -a . . veth0     Link encap:Ethernet HWaddr 5E:2C:E6:03:D0:17           BROADCAST MULTICAST  MTU:1500 Metric:1           RX packets:0 errors:0 dropped:0 overruns:0 frame:0           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000           RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b) veth1     Link encap:Ethernet HWaddr E6:B6:E2:6D:42:B8           BROADCAST MULTICAST  MTU:1500 Metric:1           RX packets:0 errors:0 dropped:0 overruns:0 frame:0           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000           RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b) . . To make the example more meaningful this we will create the following setup: veth0 => veth1 => br-eth3 => eth3 ======> eth2 on another Linux server br-eth3 – a regular Linux bridge which will be connected to veth1 and eth3 eth3 – a physical interface with no IP on it, connected to a private network eth2 – a physical interface on the remote Linux box connected to the private network and configured with the IP of 50.50.50.1 Once we create the setup we will ping 50.50.50.1 (the remote IP) through veth0 to test that the connection is up: # brctl addbr br-eth3 # brctl addif br-eth3 eth3 # brctl addif br-eth3 veth1 # brctl show bridge name     bridge id               STP enabled     interfaces br-eth3         8000.00505682e7f6       no              eth3                                                         veth1 # ifconfig veth0 50.50.50.50 # ping -I veth0 50.50.50.51 PING 50.50.50.51 (50.50.50.51) from 50.50.50.50 veth0: 56(84) bytes of data. 64 bytes from 50.50.50.51: icmp_seq=1 ttl=64 time=0.454 ms 64 bytes from 50.50.50.51: icmp_seq=2 ttl=64 time=0.298 ms When the naming is not as obvious as the previous example and we don't know who are the paired veth interfaces we can use the ethtool command to figure this out. The ethtool command returns an index we can look up using ip link command, for example: # ethtool -S veth1 NIC statistics: peer_ifindex: 12 # ip link . . 12: veth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 Summary That’s all for now, we quickly reviewed OVS, network namespaces, Linux bridges and veth pairs. These components are heavily used in the OpenStack network architecture we are exploring and understanding them well will be very useful when reviewing the different use cases. In the next post we will look at how the OpenStack network is laid out connecting the virtual machines to each other and to the external world. @RonenKofman

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