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  • What constitutes explicit creation of entities in LINQ to SQL? What elegant "solutions" are there to

    - by Marcelo Zabani
    Hi SO, I've been having problems with the rather famous "Explicit construction of entity type '##' in query is not allowed." error. Now, for what I understand, this exists because if explicit construction of these objects were allowed, tracking changes to the database would be very complicated. So I ask: What constitutes the explicit creation of these objects? In other terms: Why can I do this: Product foo = new Product(); foo.productName = "Something"; But can't do this: var bar = (from item in myDataContext.Products select new Product { productName = item.productName }).ToList(); I think that when running the LINQ query, some kind of association is made between the objects selected and the table rows retrieved (and this is why newing a Product in the first snippet of code is no problem at all, because no associations were made). I, however, would like to understand this a little more in depth (and this is my first question to you, that is: what is the difference from one snippet of code to another). Now, I've heard of a few ways to attack this problem: 1) The creation of a class that inherits the linq class (or one that has the same properties) 2) Selecting anonymous objects And this leads me to my second question: If you chose one of the the two approaches above, which one did you choose and why? What other problems did your approach introduce? Are there any other approaches?

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  • Can I delete a differential backup from SQL Server 2005?

    - by BlueMonkMN
    I often like to create backups when testing the software I work on, and will sometimes create a differential backup if I want to be able to get back to multiple previous states. However, sometimes I realize that I forgot one thing I wanted to include in a differential backup, or I no longer need a previous differential backup. Sometimes I simply want to create a new scenario from the original base image and start working with a new series of differential backups. So I'd like to be able to delete some older differential backups so I don't get confused about which ones I'm using. But I can't find any way to delete just the differential backups, selectively or all at once.

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  • sql: how to use count for a particular column ,(or) to count a particular column by its field name

    - by Aravintha Bashyam
    in my query i need a to count a particular column by its field name, SELECT C.INC_COUNT, MIN_X, MIN_Y, MAX_X, MAX_Y, B.STATE_ABBR, B.STATE_NAME, B.LATITUDE, B.LONGITUDE, A.STATE, GEO_ID, concat(A.LSAD_TRANS,' ' , A.NAME) DIST_NAME, A.LSAD, GeometryType(SHAPE) GEO_TYPE, AsText(SHAPE) GEOM from SHAPE_LAYERS A join SHAPE_LAYER_STATE_DESC B on ( A.state = B.state) left outer join INC_DIST_SUMMARY_ALL C on (C.SHAPE_GEO_ID = A. GEO_ID) here i have to count by B.STATE_NAME ,C.INC_COUNT if exmple the field name nevada means i have to get all neveda value count and the C.INC_COUNT.

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  • Which browsers support html5 offline storage?

    - by Marcin
    Essentially, I wanted to run a piece of demo code from W3c Offline Webapps page. It looks like that: var db = window.openDatabase("notes", "", "The Example Notes App!", 1048576); Firefox 3.5, IE8 and Chrome do not seem to get it. Is there anybody out there that actually wrote support for that? Or is this wishful thinking about 'the standard of the future'?

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  • Which kind of changes can't I do with lightweight migration in Core Data?

    - by dontWatchMyProfile
    I recently tried a lot of different stuff with lightweight migration. These all work: 1) Rename attributes (with renaming identifier specified) 2) Add attributes 3) Add new entity + new attribute + inverse relationship to an already existing entity 4) remove existing entity + relationships to that entity = It almost looks like just about anything can be handled with LM. Did I miss something? In which cases am I getting into trouble and need an some more complex approach?

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  • How can I sum a group of sums? SQL-Sever 2008

    - by billynomates
    I have a query with a sum in it like this: SELECT Table1.ID, SUM(Table2.[Number1] + Table2.[Number2]) AS SumColumn FROM Table1 INNER JOIN Table3 ON Table1.ID = Table3.ID INNER JOIN Table2 ON Table3.ID = Table2.ID WHERE (Table2.[Something] = 'Whatever') GROUP BY Table1.ID, Table2.[Number1] , Table2.[Number2] and it gives me a table like this: ID SumColumn 67 1 67 4 70 2 70 6 70 3 70 6 80 5 97 1 97 3 How can I make it give me a table like this, where the SumColumn is summed, grouped by the ID column? ID SumColumn 67 5 70 17 80 5 97 4 I cannot GROUP BY SumColumn because I get an error (Invalid column name 'SumColumn'.) COALESCE doesn't work either. Thanks in advance. EDIT: Just grouping by the ID gives me an error: [Number1, Number2 and the other column names that I'm selecting] is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

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  • How to query by recent date and value in SQL?

    - by wsb3383
    I have a table with three columns: patient_id, obs_date, and weight_val. patient_id stores patient identification #, weight_val stores a weight value, and obs_date stores the date when the weight reading was taken. So, a patient can have many different weight readings at different dates. How do you write a query for: select all patients whose last weight reading is 120?

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  • Using AWS S3 for photo storage

    - by Sam
    I'm going to be using S3 to store user uploaded photos. Obviously, I wont be serving the image files to user agents without resizing them down. However, not one size would do, as some thumbnails will be smaller than other larger previews. So, I was thinking of making a standard set of dimensions scaling from the lowest 16x16 to some highest 1024x1024. Is this a good way to solve this problem? What if I need a new size later on? How would you solve this?

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  • [MS Access 2003 SQL] Switch is causing #error, why and how can I fix it...

    - by Chris
    I have 3 fields in my table: start, end (dates) and length (number, might be blank). My Aim is to calculate an end date using start and length where end doesn't exist... I have: SELECT Switch((g.length<>0) And IsDate(g.end),DateAdd("m",g.length,g.start)) AS field FROM table g If there is no start, end or length, Access displays blank - this is fine. If there is no end, but start and length are ok, the calculated date is shown - again fine. BUT If there is no end, or length, but a start exists, access displays #Error I don't understand why, and can't fix it, please help!

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  • Why would SQL be very slow when doing updates?

    - by ooo
    Suddenly doing updates into a few tables have gotten 10 times slower than they used to be. What are some good recommendations to determine root cause and optimization? Could it be that indexing certain columns are causing updates to be slow? Any other recommendations? I guess more important than guesses would be help on the process of identifying the root cause or metrics around performance. Is there anything in Fluent NHibernate that you can use to help identify the root cause of performance issues?

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  • SQL Server 2003: how can I assign a name to the SUM column ?

    - by Patrick
    hi, how can I assign a column name to the SUM column ? i.e. select OwnerUserId, SUM(PostScore) INTO Experts from ... I get this error: An object or column name is missing or empty. For SELECT INTO statements, verify each column has a name. For other statements, look for empty alias names. Aliases defined as "" or [] are not allowed. Change the alias to a valid name. I guess because the column containing the results of SUM has not name. thanks

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  • SQL grouping query question; evaluating a group of rows based on the value of one field.

    - by user324575
    I've got table vendorparts that lists all my parts and their vendor(s). Parts with multiple vendors have multiple records in this table. I'm trying to write a query that only returns the partid, and vendor of parts that do not have a default vendor assigned. Partid Vendor Defaultflag 1 A 1 2 B 0 2 C 0 3 D 0 3 E 0 3 F 1 4 G 0 I would like to return the following: Partid Vendor 2 A 2 B 4 G I'm obviously having issues with partid 3 and getting the query to see it as having a default vendor assigned.

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  • extra storage merge sort

    - by davit-datuashvili
    I need make a merge sort using an additional array. Here is my code: public class extra_storage{ public static void main(String[]args) { int x[]=new int[]{12,9,4,99,120,1,3,10}; int a[]=new int[x.length]; mergesort(x,0,x.length-1,a); for (int i=0;i<x.length;i++){ System.out.println(x[i]); } } public static void mergesort(int x[],int low,int high, int a[]){ if (low>=high) { return; } int middle=(low+high)/2; mergesort(x,low,middle,a); mergesort(x,middle+1,high,a); int k; int lo=low; int h=high; for (k=low;k<high;k++) if ((lo<=middle ) && ((h>high)||(x[lo]<x[h]))){ a[k]=x[lo++]; } else { a[k]=x[h++]; } for (k=low;k<=high;k++){ x[k]=a[k]; } } } But something is wrong. When I run it the output is this: 1 0 3 0 4 0 9 0 What is the problem?

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  • Objects with inheritance memory storage

    - by nikitas350
    Say that i have some classes like this example. class A { int k, m; public: A(int a, int b) { k = a; m = b; } }; class B { int k, m; public: B() { k = 2; m = 3; } }; class C : private A, private B { int k, m; public: C(int a, int b) : A(a, b) { k = b; m = a; } }; Now, in a class C object, are the variables stored in a specific way? I know what happens in a POD object, but this is not a POD object...

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