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  • Get the count of items in a GroupBy Linq-to-sql Query?

    - by Curtis White
    I have a groupby that I groups all elements. I can see the items are there in LinqPad but can't find a way to get the count. Here is what I have so far: SurveyResponses.Where( q = q.QuestionId == 4).GroupBy(q = q.AnswerNumeric).Where( g = g.Key == 1) In Linq Pad I can see there are 4 items in this query. If I do Count it returns 1. I've tried, ToList().Count, Select(x = x).Count, etc.

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  • How to optimize this SQL query for a rectangular region?

    - by Andrew B.
    I'm trying to optimize the following query, but it's not clear to me what index or indexes would be best. I'm storing tiles in a two-dimensional plane and querying for rectangular regions of that plane. The table has, for the purposes of this question, the following columns: id: a primary key integer world_id: an integer foreign key which acts as a namespace for a subset of tiles tileY: the Y-coordinate integer tileX: the X-coordinate integer value: the contents of this tile, a varchar if it matters. I have the following indexes: "ywot_tile_pkey" PRIMARY KEY, btree (id) "ywot_tile_world_id_key" UNIQUE, btree (world_id, "tileY", "tileX") "ywot_tile_world_id" btree (world_id) And this is the query I'm trying to optimize: ywot=> EXPLAIN ANALYZE SELECT * FROM "ywot_tile" WHERE ("world_id" = 27685 AND "tileY" <= 6 AND "tileX" <= 9 AND "tileX" >= -2 AND "tileY" >= -1 ); QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------------------- Bitmap Heap Scan on ywot_tile (cost=11384.13..149421.27 rows=65989 width=168) (actual time=79.646..80.075 rows=96 loops=1) Recheck Cond: ((world_id = 27685) AND ("tileY" <= 6) AND ("tileY" >= (-1)) AND ("tileX" <= 9) AND ("tileX" >= (-2))) -> Bitmap Index Scan on ywot_tile_world_id_key (cost=0.00..11367.63 rows=65989 width=0) (actual time=79.615..79.615 rows=125 loops=1) Index Cond: ((world_id = 27685) AND ("tileY" <= 6) AND ("tileY" >= (-1)) AND ("tileX" <= 9) AND ("tileX" >= (-2))) Total runtime: 80.194 ms So the world is fixed, and we are querying for a rectangular region of tiles. Some more information that might be relevant: All the tiles for a queried region may or may not be present The height and width of a queried rectangle are typically about 10x10-20x20 For any given (world, X) or (world, Y) pair, there may be an unbounded number of matching tiles, but the worst case is currently around 10,000, and typically there are far fewer. New tiles are created far less frequently than existing ones are updated (changing the 'value'), and that itself is far less frequent that just reading as in the query above. The only thing I can think of would be to index on (world, X) and (world, Y). My guess is that the database would be able to take those two sets and intersect them. The problem is that there is a potentially unbounded number of matches for either for either of those. Is there some other kind of index that would be more appropriate?

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  • How to find a duplicate element in an array of shuffled consecutive integers?

    - by SysAdmin
    I recently came across a question somewhere Suppose you have an array of 1001 integers. The integers are in random order, but you know each of the integers is between 1 and 1000 (inclusive). In addition, each number appears only once in the array, except for one number, which occurs twice. Assume that you can access each element of the array only once. Describe an algorithm to find the repeated number. If you used auxiliary storage in your algorithm, can you find an algorithm that does not require it? what i am interested to know is the second part. i.e without using auxiliary storage . do you have any idea?

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  • SQL query to return data from two separate rows in a table joined to a master table

    - by Ali
    I have a TWO tables of data with following fields table1=(ITTAG,ITCODE,ITDESC,SUPcode) table2=(ACCODE,ACNAME,ROUTE,SALMAN) This is my customer master table that contains my customer data such as customer code, customer name and so on... Every Route has a supervisor (table1=supcode) and I need to know the supervisor name in my table which both supervisor name and code exist in one table. table1 has contain all names separated by ITTAG. For example, supervisor's name has ITTAG='K'; also salesman's name has ITTAG='S'. ITTAG ITCODE ITDESC SUPCODE ------ ------ ------ ------- S JT JOHN TOMAS TF K WK VIKI KOO NULL Now this is the result which I want ACCODE ACNAME ROUTE SALEMANNAME SUPERVISORNAME ------- ------ ------ ------------ --------------- IMC1010 ABC HOTEL 01 JOHN TOMAS VIKI KOO I hope this this information is sufficient to get the query..

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  • SQL Server: Primary Key Schema Largely Guid but Sometimes Integer Types...

    - by Code Sherpa
    OK, this may be a silly question but... I have inherited a project and am tasked with going over the primary key relationships. The project largely uses Guids. I say "largely" because there are examples where tables use integral types to reflect enumerations. For example, dbo.MessageFolder has MessageFolderId of type int to reflect public emum MessageFolderTypes { inbox = 1, sent = 2, trash = 3, etc... } This happens a lot. There are tables with primary keys of type int which is unavoidable because of their reliance on enumerations and tables with primary keys of type Guid which reflect the primary key choice on the part of the previous programmer. Should I care that the PK schema is spotty like this? It doesn't feel right but does it really matter? If this could create a problem, how do I get around it (I really can't move all PKs to type int without serious legwork and I have never heard of enumerations that have guid values)? Thanks.

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  • Any good GUI tool to easily create stored procs SQL server 2008 ?

    - by Munish Goyal
    The templates for stored-procs in SSMS do not auto-populate all input columns, again there is manual work involved. I am looking for something like right-click on table and say CREATE stored-proc, and then it allows to pick a template, based on which it can populate the parameters etc. and give check-box in GUI (like table designer, you can easily add/remove a column). Some support for change management with table undergoing alter or otherwise would also be helpful. Currently we manually write all stored-procs, which i think we should be able to save time and labor with automation. Any suggestion on other free 3rd party tools ?

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  • How do I detect a loop in this linked list?

    - by jjujuma
    Say you have a linked list structure in Java. It's made up of Nodes: class Node { Node next; // some user data } and each Node points to the next node, except for the last Node, which has null for next. Say there is a possibility that the list can contain a loop - i.e. the final Node, instead of having a null, has a reference to one of the nodes in the list which came before it. What's the best way of writing boolean hasLoop(Node first) which would return true if the given Node is the first of a list with a loop, and false otherwise? How could you write so that it takes a finite amount of space and a reasonable amount of time?

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  • An attempt has been made to Attach or Add an entity that is not new Linq to Sql error

    - by Collin Oconnor
    I have a save function for my order entity that looks like this and it breaks on the sumbmitChanges line: public void SaveOrder ( Order order ) { if (order.OrderId == 0) orderTable.InsertOnSubmit(order); else if (orderTable.GetOriginalEntityState(order) == null) { orderTable.Attach(order); orderTable.Context.Refresh(RefreshMode.KeepCurrentValues , order); } orderTable.Context.SubmitChanges(); } The order entity contains two other entities; an Address entity and a credit card entity. Now i want these two entities to be null sometimes. Now my guess for why this is throwing an error is because that both of these entites that are inside order are null. If this is the case, How can I insert an new order into the database with both entities (Address and creditCard) being null.

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  • SSRS Errors "Use Local", even though I am

    - by Corey Coogan
    I am at a loss. I posted this on SO, but think this is probably a better place. I have searched high and low and don't know what to do. I am running SQL Server Web Edition on Server 2008, which only supports local databases. I am trying to connect to localhost, but when I test my connection, I get this error. The feature: "The edition of Reporting Services that you are using requires that you use local SQL Server relational databases for report data sources and the report server database." is not supported in this edition of Reporting Services. The DB was upgraded from SQL Express and when I select @@version, it says it's Web Edition. I've tried rebooting and that seemed to fix it, but only for a little while.

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  • Want to build simple SQL admin interface to change a few values in a table.

    - by Adam McC
    i am currently building a system in MSSQL 2K5. i have a table that holds information about certain insurance schemes such as overheads and other things. these values will change occasionally and currently i administer the database straight through the management Studio. i would like to build a simple interface that will allow my colleagues to change these values by selecting the company in a dropdown and the current values will populate. they can then edit these values and submit them to the database. is this possible in the current Visual Studio supplied with MSSQL server 2K5 or do i need to get another product. i am confident that with the help of stack overflow and google i can build this myself, but i need pointed in the right direction as to which environment would be easiest and best to start building it. Many thanks, adam

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  • SQL Server 2008 BULK INSERT causes more reads than writes. Why?

    - by sh1ng
    I've huge a table (a few billion rows) with a clustered index and two non-clustered indices. A BULK INSERT operation produces 112000 reads and only 383 writes (duration 19948ms). It's very confusing to me. Why do reads exceed writes? How can I reduce it? update query insert bulk DenormalizedPrice4 ([DP_ID] BigInt, [DP_CountryID] Int, [DP_OperatorID] SmallInt, [DP_OperatorPriceID] BigInt, [DP_SpoID] Int, [DP_TourTypeID] Int, [DP_CheckinDate] Date, [DP_CurrencyID] SmallInt, [DP_Cost] Decimal(9,2), [DP_FirstCityID] Int, [DP_FirstHotelID] Int, [DP_FirstBuildingID] Int, [DP_FirstHotelGlobalStarID] Int, [DP_FirstHotelGlobalMealID] Int, [DP_FirstHotelAccommodationTypeID] Int, [DP_FirstHotelRoomCategoryID] Int, [DP_FirstHotelRoomTypeID] Int, [DP_Days] TinyInt, [DP_Nights] TinyInt, [DP_ChildrenCount] TinyInt, [DP_AdultsCount] TinyInt, [DP_TariffID] Int, [DP_DepartureCityID] Int, [DP_DateCreated] SmallDateTime, [DP_DateDenormalized] SmallDateTime, [DP_IsHide] Bit, [DP_FirstHotelAccommodationID] Int) with (CHECK_CONSTRAINTS) No triggers & foreign keys Cluster Index by DP_ID and two non-unique indexes(with fillfactor=90%) And one more thing DB stored on RAID50 with stripe size 256K

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  • Understanding the concept of inheritance in Java

    - by Nirmal
    Hello All.... I am just refreshing the oops features of the java. So, I have a little confusion regarding inheritance concept. For that I have a following sample code : class Super{ int index = 5; public void printVal(){ System.out.println("Super"); } } class Sub extends Super{ int index = 2; public void printVal(){ System.out.println("Sub"); } } public class Runner { public static void main(String args[]){ Super sup = new Sub(); System.out.println(sup.index+","); sup.printVal(); } } Now above code is giving me output as : 5,Sub. Here, we are overriding printVal() method, so that is understandable that it is accessing child class method only. But I could not understand why it's accessing the value of x from Super class... Thanks in advance....

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  • Doing a join across two databases with different collations on SQL Server and getting an error.

    - by Andrew G. Johnson
    I know, I know with what I wrote in the question I shouldn't be surprised. But my situation is slowly working on an inherited POS system and my predecessor apparently wasn't aware of JOINs so when I looked into one of the internal pages that loads for 60 seconds I see that it's a fairly quick, rewrite these 8 queries as one query with JOINs situation. Problem is that besides not knowing about JOINs he also seems to have had a fetish for multiple databases and surprise, surprise they use different collations. Fact of the matter is we use all "normal" latin characters that English speaking people would consider the entire alphabet and this whole thing will be out of use in a few months so a bandaid is all I need. Long story short is I need some kind of method to cast to a single collation so I can compare two fields from two databases. Exact error is: Cannot resolve the collation conflict between "SQL_Latin1_General_CP850_CI_AI" and "SQL_Latin1_General_CP1_CI_AS" in the equal to operation.

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  • What is the difference between "LINQ to Entities", "LINQ to SQL" and "LINQ to Dataset".

    - by Marcel
    I've been working for quite a while now with LINQ. However, it remains a bit of a mystery what the real differences are between the mentioned flavours of LINQ. The successful answer will contain a short differentiation between them. What is the main goal of each flavor, what is the benefit, and is there a performance impact... P.S. I know that there are a lot of information sources out there, but I'm looking for a kind of a "cheat sheet" which instructs a newbie where to head for a specific goal.

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  • Generating my own SQL Server SSL Certificate

    - by Haoest
    I hear it's possible to make myself a test certificate with MakeCert from Windows SDK, but the beast is 1.5 GB, which I feel reluctant to download for a half-megabyte program. I do, however, have IIS Resource kit with me, which has selfssl to generate certificate for IIS. Will that work for SQL Server? Is there a more convenient way of generating myself an SSL certificate for SQL Server use? I even tried using CREATE CERTIFICATE with TSQL within SQL Server and then have it BACKUP into a file, but with no success. I must have confused the concept of certificate fundamentally. Any advice?

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  • read-only memory and heap memory

    - by benjamin button
    hi, AFAIK, string literals are stored in read only memory in case of C language. where is this actually present on the hardware. as per my knowledge heap is on RAM.correct me if i am wrong. how different is heap from read only memory? is it OS dependant?

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  • MySql Query lag time?

    - by Click Upvote
    When there are multiple PHP scripts running in parallel, each making an UPDATE query to the same record in the same table repeatedly, is it possible for there to be a 'lag time' before the table is updated with each query? I have basically 5-6 instances of a PHP script running in parallel, having been launched via cron. Each script gets all the records in the items table, and then loops through them and processes them. However, to avoid processing the same item more than once, I store the id of the last item being processed in a seperate table. So this is how my code works: function getCurrentItem() { $sql = "SELECT currentItemId from settings"; $result = $this->db->query($sql); return $result->get('currentItemId'); } function setCurrentItem($id) { $sql = "UPDATE settings SET currentItemId='$id'"; $this->db->query($sql); } $currentItem = $this->getCurrentItem(); $sql = "SELECT * FROM items WHERE status='pending' AND id > $currentItem'"; $result = $this->db->query($sql); $items = $result->getAll(); foreach ($items as $i) { //Check if $i has been processed by a different instance of the script, and if so, //leave it untouched. if ($this->getCurrentItem() > $i->id) continue; $this->setCurrentItem($i->id); // Process the item here } But despite of all the precautions, most items are being processed more than once. Which makes me think that there is some lag time between the update queries being run by the PHP script, and when the database actually updates the record. Is it true? And if so, what other mechanism should I use to ensure that the PHP scripts always get only the latest currentItemId even when there are multiple scripts running in parrallel? Would using a text file instead of the db help?

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  • 3 page longest path on a website

    - by Kazoom
    i have a log file which maintains source entry for each page.all the pages share the common file. source means from what page did user arrive on the target page. I want to find the most common 3 page path for all the pages on the website. Example log file: source Target 1 2 1 3 2 1 3 2 3 2 2 1 The most common 3 page path here was from 3 to 2 to 1.

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  • Data access strategy for a site like SO - sorted SQL queries and simultaneous updates that affect th

    - by Kaleb Brasee
    I'm working on a Grails web app that would be similar in access patterns to StackOverflow or MyLifeIsAverage - users can vote on entries, and their votes are used to sort a list of entries based on the number of votes. Votes can be placed while the sorted select queries are being performed. Since the selects would lock a large portion of the table, it seems that normal transaction locking would cause updates to take forever (given enough traffic). Has anyone worked on an app with a data access pattern such as this, and if so, did you find a way to allow these updates and selects to happen more or less concurrently? Does anyone know how sites like SO approach this? My thought was to make the sorted selects dirty reads, since it is acceptable if they're not completely up to date all of the time. This is my only idea for possibly improving performance of these selects and updates, but I thought someone might know a better way.

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