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  • Sqlite: Selecting records spread over total records

    - by Martin
    I have a sql / sqlite question. I need to write a query that select some values from a sqlite database table. I always want the maximal returned records to be 20. If the total selected records are more than 20 I need to select 20 records that are spread over the total records. It is also important that I always select the first and last value from the table when sorted on the date. I know how to accomplish this in code but it would be perfect to have a sqlite query that can do the same. The query Im using now is really simple and looks like this: "SELECT value,date,valueid FROM tblvalue WHERE tblvalue.deleted=0 ORDER BY DATE(date)" Hope I explained what I need, thanks for your help!

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  • Building a specific piece of Android platform?

    - by Chrisc
    Hi, I have been trying to build only the "/libcore" directory of the Android platform. When I try mmm libcore I end up with the following output: ============================================ PLATFORM_VERSION_CODENAME=REL PLATFORM_VERSION=2.1-update1 TARGET_PRODUCT=generic TARGET_BUILD_VARIANT=eng TARGET_SIMULATOR=false TARGET_BUILD_TYPE=release TARGET_ARCH=arm HOST_ARCH=x86 HOST_OS=linux HOST_BUILD_TYPE=release BUILD_ID=ECLAIR ============================================ make: Entering directory `/home/chris/android/platform' target Prebuilt: (out/target/product/generic/system/etc/security/cacerts.bks) host Prebuilt: run-core-tests-on-ri (out/host/linux-x86/obj/EXECUTABLES/run-core-tests-on-ri_intermediates/run-core-tests-on-ri) target Prebuilt: run-core-tests (out/target/product/generic/obj/EXECUTABLES/run-core-tests_intermediates/run-core-tests) Copy: out/target/product/generic/system/etc/apns-conf.xml Copying: out/target/common/obj/JAVA_LIBRARIES/core_intermediates/classes-full-debug.jar Copying: out/target/common/obj/JAVA_LIBRARIES/core-tests_intermediates/classes-full-debug.jar /bin/bash: jar: command not found make: *** [out/host/common/core-tests.jar] Error 127 make: *** Deleting file `out/host/common/core-tests.jar' make: Leaving directory `/home/chris/android/platform' Does anyone have any suggestions on what Error 127 is, or another method I can go about building "libcore" without having to build the entire platform again? Thanks, Chris

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  • Converting "is null" into a linq to sql statement

    - by Darryl Braaten
    I am having trouble replicating the following sql as a LINQ statement select TableA.* from TableA left outer join TableAinTableB on TableA.Id = TableAId where TableBId is null The following returns no lines from TableA in db.TableA join AinB in db.TableAinTableB on TableA.Id equals TableAId where AinB.TableBId == null select TableA Also tried and a few other things that didn't work. from TableA in db.TableA join AinB in db.TableAinTableB on TableA.Id equals TableAId where AinB == null select TableA TableAinTableB is a many to many table. The query I want will pull all the records from TableA that have no records in the middle table. My sql does what I want but I have no idea how to convert it to LINQ to SQL. I ended up working around it by just doing a db.ExecuteQuery("working sql"); But I would like to know if the query is possible in LINQ and how to write it, or a pointer to a document that covers this scenario. My searching did not uncover anything I found useful.

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  • Thoughts on Build 2013

    - by D'Arcy Lussier
    Originally posted on: http://geekswithblogs.net/dlussier/archive/2013/06/30/153294.aspxAnd so another Build conference has come to an end. Below are my thoughts/perspectives on various aspects of the event. I’ll do a separate blog post on my thoughts of the Build message for developers. The Good Moscone center was a great venue for Build! Easy to get around, easy to get to, and well maintained, it was a very comfortable conference venue. Yeah, the free swag was nice. Build has built up an expectation that attendees will always get something; it’ll be interesting to see how Microsoft maintains this expectation over the next few Build events. I still maintain that free swag should never be the main reason one attends an event, and for me this was definitely just an added bonus. I’m planning on trying to use the Surface as a dedicated 2nd device at work for meetings, I’ll share my experiences over the next few months. The hackathon event was a great idea, although personally I couldn’t justify spending the money on a conference registration just to spend the entire conference coding. Still, the apps that were created were really great and there was a lot of passion and excitement around the hackathon. I wonder if they couldn’t have had the hackathon on the Monday/Tuesday for those that wanted to participate so they didn’t miss any of the actual conference over Wed/Thurs. San Francisco was a great city to host Build. Getting from hotels to the conference center was very easy (well especially for me, I was only 3 blocks away) and the city itself felt very safe. However, if I never have to fly into SFO again I’ll be alright with that! Delays going into and out of SFO and both apparently were due to the airport itself. The Bad Build is one of those oddities on the conference landscape where people will pay to commit to attending an event without knowing anything about the sessions. We got our list of conference sessions when we registered on Tuesday, not before. And even then, we only got titles and not descriptions (those were eventually made available via the conference’s mobile application). I get it…they’re going to make announcements and they don’t want to give anything away through the session titles. But honestly, there wasn’t anything in the session titles that I would have considered a surprise. Breakfasts were brutal. High-carb pastries, donuts, and muffins with fruit and hard boiled eggs does not a conference breakfast make. I can’t believe that the difference between a continental breakfast per person and a hot breakfast buffet would have been a huge impact to a conference fee that was already around $2000. The vendor area was anemic. I don’t know why Microsoft forces the vendors into cookie-cutter booth areas (this year they were all made of plywood material). WPC, TechEd – booth areas there allow the vendors to be creative with their displays. Not so much for Build. Really odd was the lack of Microsoft’s own representation around Bing. In the day 1 keynote Microsoft made a big deal about Bing as an API. Yet there was nobody in the vendor area set up to provide more information or have discussions with about the Bing API. The Ugly Our name badges were NFC enabled. The purpose of this, beyond the vendors being able to scan your info, wasn’t really made clear. An attendee I talked to showed how you could get a reader app on your phone so you can scan other members cards and collect their contact info – which is a kewl idea; business cards are so 1990’s. But I was *shocked* at the amount of information that was on our name badges! Here’s what’s displayed on our name badge: - Name - Company - Twitter Handle I’m ok with that. But here’s what actually gets read: - Name - Company - Address Used for Registration - Phone Number Used for Registration So sharing that info with another attendee, they get way more of my info than just how to find me on Twitter! Microsoft, you need to fix this for the future. If vendors want to collect information on attendees, they should be able to collect an ID from the badge, then get a report with corresponding records afterwards. My personal information should not be so readily available, and without my knowledge! Final Verdict Maybe its my older age, maybe its where I’m at in life with family, maybe its where I’m at in my career, but when I consider whether a conference experience was valuable I get to the core reason I attend: opportunities to learn, opportunities to network, opportunities to engage with Microsoft. Opportunities to Learn:  Sessions I attended were generally OK, with some really stand out ones on Day 2. I would love to see Microsoft adopt the Dojo format for a portion of their sessions. Hands On Labs are dull, lecture style sessions are great for information sharing. But a guided hands-on coding session (Read: Dojo) provides the best of both worlds. Being that all content is publically available online to everyone (Build attendee or not), the value of attending the conference sessions is decreased. The value though is in the discussions that take part in person afterwards, which leads to… Opportunities to Network: I enjoyed getting together with old friends and connecting with Twitter friends in person for the first time. I also had an opportunity to meet total strangers. So from a networking perspective, Build was fantastic! I still think it would have been great to have an area for ad-hoc discussions – where speakers could announce they’d be available for more questions after their sessions, or attendees who wanted to discuss more in depth on a topic with other attendees could arrange space. Some people have no problems being outgoing and making these things happen, but others are not and a structured model is more attractive. Opportunities to Engage with Microsoft: Hit and miss on this one. Outside of the vendor area, unless you cornered or reached out to a speaker, there wasn’t any defined way to connect with blue badges. And as I mentioned above, Microsoft didn’t have full representation in the vendor area (no Bing). All in all, Build was a fun party where I was informed about some new stuff and got some free swag. Was it worth the time away from home and the hit to my PD budget? I’d say Somewhat. Build is a great informational conference, but I wouldn’t call it a learning conference. Considering that TechEd seems to be moving to more of an IT Pro focus, independent developer conferences seem to be the best value for those looking to learn and not just be informed. With the rapid development cycle Microsoft is embracing, we’re already seeing Build happening twice within a 12 month period. If that continues, the value of attending Build in person starts to diminish – especially with so much content available online. If Microsoft wants Build to be a must-attend event in the future, they need to start incorporating aspects of Tech Ed, past PDCs, and other conferences so those that want to leave with more than free swag have something to attract them.

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  • ASP.Net Custom Field From Query In DataSet

    - by boruchsiper
    I added a new query to a table adapter in a DataSet. This query adds another field to the query whcih is a sum from another table. Here is the full query: SELECT (SELECT COUNT(donationID) AS Expr1 FROM Donations AS da WHERE (dn.donorID = donorID)) AS Count, Solicitor, address1, address2, city, companyName, country, donorID, email, first, last, phoneHome, phoneMobile, phoneWork, state, webURL, zip, (select sum(amount) from Donations as dna where dna.donorID = dn.donorID) as SumDonations FROM Donors AS dn order by last The new field is represented in the last part of the query: (select sum(amount) from Donations as dna where dna.donorID = dn.donorID) as SumDonations I can preview the data in the xsd but the last field "SumDonations" is not showing up as a field I can add to my gridview. I rebuilt the website but no luck. What am I missing?

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  • [MYSQL] Select users who own both a dog and a cat

    - by matte
    Hi, I have this sample table: CREATE TABLE `dummy` ( `id` int(11) NOT NULL AUTO_INCREMENT, `userId` int(11) NOT NULL, `pet` varchar(50) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=7 ; INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(1, 1, 'dog'); INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(2, 1, 'cat'); INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(3, 2, 'dog'); INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(4, 2, 'cat'); INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(5, 3, 'cat'); INSERT INTO `dummy` (`id`, `userId`, `pet`) VALUES(6, 4, 'dog'); How can I write the statements below in mysql: Retrieve all users who own both a dog and a cat Retrieve all users who own a dog or a cat Retrieve all users who own only a cat Retrieve all users who doesn't own a cat Thanks!

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  • Dynamically pulling images from XML for iPhone App

    - by Simon Hume
    I've got my iPhone app pulling down live data content via XML nicely, and I've formatted the UITableView cells to display the content without too many headaches. However, at the moment, for each cell I'm just showing a default graphic for now, but I want this to be pulled down from my server too. The code snippet that grabs the image (which is actually in my project) is: cell.imageView.image = [UIImage imageNamed:@"TBC.png"]; But that will need to be the dynamic image. In my XML, am I better just returning 'mypic.png' and let the SDK determine the full path, like http://myapp.com/mypic.png or storing the full URL to the image in the XML?

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  • jQuery: .toggle() doesnt work properly on two different elements.

    - by Marius
    Hello there, This is my markup: <table class="col1table" cellspacing="0" cellpadding="0"> <tr> <td><a class="tips_trigger" href="#"><img src="/img/design/icon_tips_venn.png" /></a></td> <td><a class="facebook_trigger" href="#"><img src="/img/design/icon_facebook.png" /></a></td> <td><a class="twitter_trigger" href="#"><img src="/img/design/icon_twitter.png" /></a></td> <td><a class="myspace_trigger" href="#"><img src="/img/design/icon_myspace.png" /></a></td> </tr> <tr> <td><a class="tips_trigger" href="#">TIPS EN VENN</a></td> <td><a class="facebook_trigger" href="#">FACEBOOK</a></td> <td><a class="twitter_trigger" href="#">TWITTER</a></td> <td><a class="myspace_trigger" href="#">MYSPACE</a></td> </tr> </table> This is the mark-up for a tool-tip: <div id="message_tips" class="toolTip">Lorem ipsum dolor sit amet.<br /><br /><br /><br /><br /><br />Lorem ipsum dolor sit amet.</div> This is my code to hide/unhide tooltip for .tips_trigger (the tooltip has id: "#message_tips"). Notice that there is one .tips_trigger on each row in the table. And there will be one tooltip per "..._trigger-class". $('.tips_trigger').toggle(function(event){ event.preventDefault(); $('#message_tips').css('display', 'block'); }, function(event){ $('#message_tips').css('display', 'none'); }); I have two problems: 1. Each of the tips_trigger-classes seems to work the script independatly. What I mean by that is if I click tips_trigger in the first row, it displays the tool-tip. If i click tips_trigger in the second row straight after, it displays the tool-tip again. I have to click the exact same tips_trigger-class istance twice for it to hide it. How can I overcome this problem? 2. Each of the "..._trigger"-classes will have a tool-tip, not just ".tips_trigger". Is there a way to alter my current script so that it works for multiple unhides/hides instead of writing one script per class? Kind regards, Marius

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  • Help with hash tables and quadratic probing in Java

    - by user313458
    I really need help with inserting into a hash table. I'm just not totally getting it right now. Could someone explain quadratic and linear probing in layman's terms? public void insert(String key) { int homeLocation = 0; int location = 0; int count = 0; if (find(key).getLocation() == -1) // make sure key is not already in the table { //****** ADD YOUR CODE HERE FOR QUADRATIC PROBING ******** } } This is the code I'm working on. I'm not asking anyone to do it, I just really need help with learning the whole concept Any help would be greatly appreciated.

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  • PHP/MySQL User system w/ groups.

    - by Ben C
    I have a user system set up in a 'users' table, and I have groups set up in a 'groups' table. Essentially, I want users to be able to join any and all the groups that they want, in the same was as one would on facebook. How would one go about structuring this in a mysql/php database system? Just a quick summary would be helpful! I've looked around, but I can only find info on creating 'groups' where the users just have a sort of 1, 2 or 3 permission rank. Thanks!

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  • Reduce Multiple Errors logging in sysssislog

    - by Akshay
    Need help. I am trying to automate error notifications to be sent in mailers. For that I am querying the sysssislog table. I have pasted an "Execute SQl task" on the package event handler "On error". For testing purpose, I am deliberately trying to load duplicate keys in a table which consists of a Primary key column(so as to get an error). But instead of having just one error, "Violation of primary key constraint", SSIS records 3 in the table. PFA the screenshot as well. How can i restrict the tool to log only one error and not multiple ??? Package Structure. Package ("On error Event handler") - DFT - Oledb Source - Oledb Destination SSIS Error Code DTS_E_OLEDBERROR. An OLE DB error has occurred. Error code: 0x80004005. An OLE DB record is available. Source: "Microsoft SQL Server Native Client 10.0" Hresult: 0x80004005 Description: "The statement has been terminated.". An OLE DB record is available. Source: "Microsoft SQL Server Native Client 10.0" Hresult: 0x80004005 Description: "Violation of PRIMARY KEY constraint 'PK_SalesPerson_SalesPersonID'. Cannot insert duplicate key in object 'dbo.SalesPerson'.". SSIS Error Code DTS_E_INDUCEDTRANSFORMFAILUREONERROR. The "input "OLE DB Destination Input" (56)" failed because error code 0xC020907B occurred, and the error row disposition on "input "OLE DB Destination Input" (56)" specifies failure on error. An error occurred on the specified object of the specified component. There may be error messages posted before this with more information about the failure. SSIS Error Code DTS_E_PROCESSINPUTFAILED. The ProcessInput method on component "OLE DB Destination" (43) failed with error code 0xC0209029 while processing input "OLE DB Destination Input" (56). The identified component returned an error from the ProcessInput method. The error is specific to the component, but the error is fatal and will cause the Data Flow task to stop running. There may be error messages posted before this with more information about the failure. Please guide me. Your help is very much appreciated. Thanks

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  • Get forum page by PostID

    - by cem
    I can't figure out how it's working. Like this. How is this get page number -and records- by post id? I think the first option is; declare an index / int variable in post table and increase-decrease it when adding and deleting post. but whats happen when i delete first row and if table has one million records? Do you have any idea about this? by the way, i'm using nhibernate and sql server 2005. Thank you

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  • Recommendation needed for text content, should I use text files or database?

    - by Jörgen
    I'm doing a web application in asp.net mvc. Now I'm at the point where I do alot of text info such as help texts, eula, privacy policy etc. I realized that I'm not sure what would the best way to store these texts. 1. Directly in the aspx page 2. In text files and then load the text via ViewData[] to the aspx file 3. In my sql database If use option 3 how would I then design the database e.g. eula = table x, privacypolicy=table y? I guess I just need some directions of what't the pros and cons with the options above.

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  • How to prevent column b containing the same value as any column a in Oracle?

    - by Janek Bogucki
    What is a good way to prevent a table with 2 columns, a and b, from having any record where column b is equal to any value in column a? This would be used for a table of corrections like this, MR -> Mr Prf. -> Prof. MRs -> Mrs I can see how it could be done with a trigger and a subquery assuming no concurrent activity but a more declarative approach would be preferable. This is an example of what should be prevented, Wing Commdr. -> Wing Cdr. Wing Cdr. -> Wing Commander Ideally the solution would work with concurrent inserts and updates.

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  • Shortest-path algorithms which use a space-time tradeoff?

    - by Chris Mounce
    I need to find shortest paths in an unweighted, undirected graph. There are algorithms which can find a shortest path between two nodes, but this can take time. There are also algorithms for computing shortest paths for all pairs of nodes in the graph, but storing such a lookup table would take lots of disk space. What I'm wondering: Is there an algorithm which offers a space-time tradeoff that's somewhere between these two extremes? In other words, is there a way to speed up a shortest-path search, while using less disk space than would be occupied by an all-pairs shortest-path table? I know there are ways to efficiently store lookup tables for this problem, and I already have a couple of ideas for speeding up shortest-path searches using precomputed data. But I don't want to reinvent the wheel if there's already some established algorithm that solves this problem.

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  • How do I set ORDER BY params using prepated PDO statement?

    - by Marlorn
    I'm having problems using params in the ORDER BY section of my SQL. It doesn't issue any warnings, but prints out nothing. $order = 'columnName'; $direction = 'ASC'; $stmt = $db->prepare("SELECT field from table WHERE column = :my_param ORDER BY :order :direction"); $stmt->bindParam(':my_param', $is_live, PDO::PARAM_STR); $stmt->bindParam(':order', $order, PDO::PARAM_STR); $stmt->bindParam(':direction', $direction, PDO::PARAM_STR); $stmt->execute(); The :my_param works, but not :order or :direction. Is it not being internally escaped correctly? Am I stuck inserting it directly in the SQL? Like so: $order = 'columnName'; $direction = 'ASC'; $stmt = $db->prepare("SELECT * from table WHERE is_live = :is_live ORDER BY $order $direction"); Is there a PDO::PARAM_COLUMN_NAME constant or some equivalent? Thanks!

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  • How to salvage SQL server 2008 query from KILLED/ROLLBACK state?

    - by littlegreen
    I have a stored procedure that inserts batches of millions of rows, emerging from a certain query, into an SQL database. It has one parameter selecting the batch; when this parameter is omitted, it will gather a list of batches and recursively call itself, in order to iterate over batches. In (pseudo-)code, it looks something like this: CREATE PROCEDURE spProcedure AS BEGIN IF @code = 0 BEGIN ... WHILE @@Fetch_Status=0 BEGIN EXEC spProcedure @code FETCH NEXT ... INTO @code END END ELSE BEGIN -- Disable indexes ... INSERT INTO table SELECT (...) -- Enable indexes ... Now it can happen that this procedure is slow, for whatever reason: it can't get a lock, one of the indexes it uses is misdefined or disabled. In that case, I want to be able kill the procedure, truncate and recreate the resulting table, and try again. However, when I try and kill the procedure, the process frequently oozes into a KILLED/ROLLBACK state from which there seems to be no return. From Google I have learned to do an sp_lock, find the spid, and then kill it with KILL <spid>. But when I try to kill it, it tells me SPID 75: transaction rollback in progress. Estimated rollback completion: 0%. Estimated time remaining: 554 seconds. I did find a forum message hinting that another spid should be killed before the other one can start a rollback. But that didn't work for me either, plus I do not understand, why that would be the case... could it be because I am recursively calling my own stored procedure? (But it should be having the same spid, right?) In any case, my process is just sitting there, being dead, not responding to kills, and locking the table. This is very frustrating, as I want to go on developing my queries, not waiting hours on my server sitting dead while pretending to be finishing a supposed rollback. Is there some way in which I can tell the server not to store any rollback information for my query? Or not to allow any other queries to interfere with the rollback, so that it will not take so long? Or how to rewrite my query in a better way, or how kill the process successfully without restarting the server?

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  • SQL-query task, decision?

    - by Sirius Lampochkin
    There is a table of currencies rates in MS SQL Server 2005: ID | CURR | RATE | DATE 1   | USD   | 30      | 01.10.2010 3   | GBP   | 45      | 07.10.2010 5   | USD   | 31      | 08.10.2010 7   | GBP   | 46      | 09.10.2010 9   | USD   | 32      | 12.10.2010 11 | GBP   | 48      | 03.10.2010 Rate are updated in real time and there are more than 1 billion rows in the table. It needs to write a SQL-query, wich will provide latest rates per each currency. My decision is: SELECT c.[id],c.[curr],c.[rate],c.[date] FROM [curr_rate] c, (SELECT curr, MAX(date) AS rate_date FROM [curr_rate] GROUP BY curr) t WHERE c.date = t.rate_date AND c.curr = t.curr ORDER BY c.[curr] ASC Is it possible to write a query without sub-queries and join's with derived tables?

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  • Representing Sparse Data in PostgreSQL

    - by Chris S
    What's the best way to represent a sparse data matrix in PostgreSQL? The two obvious methods I see are: Store data in a single a table with a separate column for every conceivable feature (potentially millions), but with a default value of NULL for unused features. This is conceptually very simple, but I know that with most RDMS implementations, that this is typically very inefficient, since the NULL values ususually takes up some space. However, I read an article (can't find its link unfortunately) that claimed PG doesn't take up data for NULL values, making it better suited for storing sparse data. Create separate "row" and "column" tables, as well as an intermediate table to link them and store the value for the column at that row. I believe this is the more traditional RDMS solution, but there's more complexity and overhead associated with it. I also found PostgreDynamic, which claims to better support sparse data, but I don't want to switch my entire database server to a PG fork just for this feature. Are there any other solutions? Which one should I use?

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  • How to modify the attributes by putting dynamic node paths

    - by sam
    I have a code that selects all elements and their child nodes DECLARE @x XML DECLARE @node_no int DECLARE @count int DECLARE @max INT, @i INT EXECUTE return_xml '1', NULL, @x output Declare @temp Table ( id int not null identity(1,1), ParentNodeName varchar(max), NodeName varchar(max), NodeText varchar(max) ) INSERT INTO @temp SELECT t.c.value('local-name(..)', 'varchar(max)') AS ParentNodeName, t.c.value('local-name(.)', 'varchar(max)') AS NodeName, t.c.value('text()[1]', 'varchar(max)') AS NodeText FROM @x.nodes('/booking//*') AS t(c) select * from @temp Now I want to modify the attributs by putting dynamic node paths SET @x.modify (' insert attribute MyId {sql:variable("@i")} as first into (ParentNodeName/NodeName::*[position() = sql:variable("@i")])[1] ') where id = id of temp table any Idea how can I modify my whole xml this way as I am having a untyped xml and have to add an attribute in every node

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  • Why is my iPhone SDK 3.2 iPad code showing a white screen?

    - by Anthony Glyadchenko
    I'm trying to get a UISplitViewController working with an iPad app. I have the table view controller linked up under the Master pane and a plain UIView under the Detail view. I also have [window addSubview:splitView.view]; in my code. For some reason I just get a white screen even though the table view controller code is properly coded and linked under my nib. Any help would be great! Thanks! Here's where you can find the code: http://drop.io/s28bu4t/asset/mydevice-hd-zip

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  • How can i query for null values in entity framework?

    - by AZ
    I want to execute a query like this var result = from entry in table where entry.something == null select entry; and get an IS NULL generated. Edited: After the first two answers i feel the need to clarify that I'm using Entity Framework and not Linq to SQL. The object.Equals() method does not seem to work in EF. Edit no.2: The above query works as intended. It correctly generates IS NULL. My production code however was var value = null; var result = from entry in table where entry.something == value select entry; and the generated SQL was something = @p; @p = NULL. It seems that EF correctly translates the constant expression but if a variable is involved it treats it just like a normal comparison. Makes sense actually. I'll close this question

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  • Sequence numbers best practice

    - by Abdullah Jibaly
    What's the best practice or well known methods to implement sequence numbers for business entities such as invoices, purchase orders, job numbers, etc? I want to be able to save the latest value in the database and be able to set it programatically. Is it OK to use a table for this purpose that has a SEQUENCE_NAME, SEQUENCE_NUMBER tuple? I know some databases have a first class sequence type but others (eg, MySQL) do not so it's not something I want to rely on. If a table is used to hold these sequences what is the right way to get and increment them in a synchronized fashion to ensure no data inconsistencies arise?

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  • Is java HashMap.clear() and remove() memory effective?

    - by Shaman
    Consider the follwing HashMap.clear() code: /** * Removes all of the mappings from this map. * The map will be empty after this call returns. */ public void clear() { modCount++; Entry[] tab = table; for (int i = 0; i < tab.length; i++) tab[i] = null; size = 0; } It seems, that the internal array (table) of Entrys is never shrinked. So, when I add 10000 elements to a map, and after that call map.clear(), it will keep 10000 nulls in it's internal array. So, my question is, how does JVM handle this array of nothing, and thus, is HashMap memory effective?

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