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  • Entity Framework doesn't like 0..1 to * relationships.

    - by Orion Adrian
    I have a database framework where I have two tables. The first table has a single column that is an identity and primary key. The second table contains two columns. One is a nvarchar primary key and the other is a nullable foreign key to the first table. On the default import of the database I get the following error: Condition cannot be specified for Column member 'ForeignKeyId' because it is marked with a 'Computed' or 'Identity' StoreGeneratedPattern. where ForeignKeyId is the second foreign key reference in the second table. Is this just something the entity model doesn't do? Or am I missing something?

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  • Select Statements in Jobs

    - by Andrew Vogel
    I have inherited a few jobs and I am trying to understand why select statements would be in their steps. I would think that select statements would be pointless in an automated job that displays nothing for an end user.

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  • Index on column with only 2 distinct values

    - by Will
    I am wondering about the performance of this index: I have an "Invalid" varchar(1) column that has 2 values: NULL or 'Y' I have an index on (invalid), as well as (invalid, last_validated) Last_validated is a datetime (this is used for a unrelated SELECT query) I am flagging a small amount of items (1-5%) of rows in the table with this as 'to be deleted'. This is so when i DELETE FROM items WHERE invalid='Y' it does not perform a full table scan for the invalid items. A problem seems to be, the actual DELETE is quite slow now, possibly because all the indexes are being removed as they are deleted. Would a bitmap index provide better performance for this? or perhaps no index at all?

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  • Does the optimizer filter subqueries with outer where clauses

    - by Mongus Pong
    Take the following query: select * from ( select a, b from c UNION select a, b from d ) where a = 'mung' Will the optimizer generally work out that I am filtering a on the value 'mung' and consequently filter mung on each of the queries in the subquery. OR will it run each query within the subquery union and return the results to the outer query for filtering (as the query would perhaps suggest) In which case the following query would perform better : select * from ( select a, b from c where a = 'mung' UNION select a, b from d where a = 'mung' ) Obviously query 1 is best for maintenance, but is it sacrificing much performace for this? Which is best?

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  • How Can I Generate Random Unqiue Numbers in C#

    - by peace
    public int GenPurchaseOrderNum() { Random random = new Random(); _uniqueNum = random.Next(13287, 21439); return UniqueNum; } I removed unique constraint from the PONumber column in the db because an employee should only generate P.O. # when the deal is set. Otherwise, P.O. # would have 0. P.O. Number used to have unique constraint, this forces employee to generate P.O. in all cases so the db doesn't throw unique constraint error. Since i removed the unique constraint, any quote doesn't have P.O. will carry 0 value. Otherwise, a unique value is generated for P.O. #. However, i don't have a unique constraint in db which makes it hard for me to know whether the application generated P.O. # is unique or not. What should i do? I hope my question is clear enough

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  • Active Record/ORM vs Normal Forms?

    - by Arsenal
    Hello, I've been playing around with Active Record a bit, and I have noticed that A.C./ORM always uses the following database model when creating a one-to-one relationship Person id | country_id | name | ... Country id | tld | name | ... No I wondered, isn't this a violiation of the third Normal Form? This clearly states "Every non-prime attribute is non-transitively dependent on every key of the table". Well this country_id isn't dependent of personid is it? So is this wrong or am I just not getting the point?

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  • How do I perform 'WHERE' on groups of rows?

    - by Drew
    I have a table, which looks like: +-----------+----------+ + person_id + group_id + +-----------+----------+ + 1 + 10 + + 1 + 20 + + 1 + 30 + + 2 + 10 + + 2 + 20 + + 3 + 10 + +-----------+----------+ I need a query such that only person_ids with groups 10 AND 20 AND 30 are returned (only person_id: 1). I am not sure how to do this, as from what I can see it would require me to group the rows by person_id and then select the rows which contain all group_ids. I'm looking for something which will preserve the use of keys without resorting to string operations on group_concat() or such.

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  • C# Getting Just Date From Timestamp

    - by Soo
    If I have a timestamp in the form: yyyy-mm-dd hh:mm:ss:mmm How can I just extract the date from the timestamp? For instance, if a timestamp reads: "2010-05-18 08:36:52:236" what is the best way to just get 2010-05-18 from it. What I'm trying to do is isolate the date portion of the timestamp, define a custom time for it to create a new time stamp. Is there a more efficient way to define the time of the timestamp without first taking out the date, and then adding a new time?

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  • Replication - syncronizing most of the data some of the time

    - by uncle brad
    I have some data that isn't properly "partitioned" (for lack of a better word). All inserts, processing and reporting happen on the same table. The bulk of the processing happens not long after the insert and not long after that it becomes immutable (we're talking days). I could do all inserts and processing on a new table that I replicate to the old table. When I detect that the data has become immutable I would delete the data from the new table, but I would edit the delete replication stored procedure so that the delete did not replicate. How bad an idea is this? It seems attractive at the moment (I haven't slept on it yet) because it might mitigate a performance problem with only very small changes to the application. It also seems like it might be a good way to shoot myself in the foot.

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  • have we limitation in submit some query in c# to oracle

    - by rima
    Can I send this query from my C# connection to my oracle connection? "Select Object_name,status from object_name where object_type='function';" or "Select Object_name,status from object_name where object_type='Procedure';" or because as I remember, I have this problem when I write a program to connect to Access with java,those days I try to submit some query to get all table name. regard.

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  • Returning IEnumerable<T> vs IQueryable<T>

    - by stackoverflowuser
    what is the difference between returning iqueryable vs ienumerable. IQueryable<Customer> custs = from c in db.Customers where c.City == "<City>" select c; IEnumerable<Customer> custs = from c in db.Customers where c.City == "<City>" select c; Will both be deferred execution? When should one be preferred over the other?

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  • Problem with LINQ in C#

    - by David Bonnici
    I am encountering a problem when using LINQ in C#, I am constantly getting "Specified cast is not valid". This is what I am trying to do. I create a class in which I declare all the columns of the table. [Table(Name="tbl_Aff")] public class Affiliate { [Column] public string name; [Column] public string firstname; [Column] public string surname; [Column] public string title; } I then declare a strongly typed DataContext in which I declare all Table collections as members of the context. public partial class Database : DataContext { public Table affiliate; public Database() : base(Settings.getConnectionString()) { } //This method gets the connection string by reading from an XML file. } public partial class Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { Database database = new Database(); try { var q = from a in database.affiliate select a; foreach (var aff in q) // Here I get the error "Specified cast is not valid" { lblMessage.InnerHtml += aff.name + ""; } } catch (Exception ex) { System.Console.WriteLine(ex.Message); } } }

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  • linq join query

    - by SamB09
    Hi, im trying to do a join in linq , however for some reason i cant access the primary key of a table. It's the 'h.ProjectId' that doesn't seem to be accepted. The following error is given CW1.SearchWebService.Bid does not contain a definition for 'ProjectId' and no extention method 'ProjectId' accepting a first argument of type 'CW1SearchWebService.Bid' var allProjects = ctxt.Project.ToList() ; var allBids = ctxt.Bid.ToArray();// return all bids var projects = (from project in allProjects join h in allBids on project.ProjectId equals h.ProjectId

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  • SqlServer2008 + expensive union

    - by Tim Mahy
    Hi al, we have 5 tables over which we should query with user search input throughout a stored procedure. We do a union of the similar data inside a view. Because of this the view can not be materialized. We are not able to change these 5 tables drastically (like creating a 6th table that contains the similar data of the 5 tables and reference that new one from the 5 tables). The query is rather expensive / slow what are our other options? It's allowed to think outside the box. Unfortunately I cannot give more information like the table/view/SP definition because of customer confidentiality... greetings, Tim

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  • Arrays in database tables and normalization

    - by Ivan Petrov
    Hi! Is it smart to keep arrays in table columns? More precisely I am thinking of the following schema which to my understanding violates normalization: create table Permissions( GroupID int not null default(-1), CategoryID int not null default(-1), Permissions varchar(max) not null default(''), constraint PK_GroupCategory primary key clustered(GroupID,CategoryID) ); and this: create table Permissions( GroupID int not null default(-1), CategoryID int not null default(-1), PermissionID int not null default(-1), constraint PK_GroupCategory primary key clustered(GroupID,CategoryID) ); UPD: Forgot to mention, in the scope of this concrete question we will consider that the "fetch rows that have permission X" won't be performed, instead all the lookups will be made by GroupID and CategoryID only Thoughts? Thanks in advance!

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  • LINQ Query returns nothing.

    - by gtas
    Why is this query returns 0 lines? There is a record matching the arguments. Deafkaw.Where(p => (p.ImerominiaKataxorisis >= aDate && p.ImerominiaKataxorisis <= DateTime.Now) && (p.Year == etos && p.IsYpodeigma == false) ).ToList(); Am i missing something?

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  • Help with SQL Query

    - by djfrear
    With regards to the following statement: Select * From explorer.booking_record booking_record_ Inner Join explorer.client client_ On booking_record_.labelno = client_.labelno Inner Join explorer.tour_hotel tour_hotel_ On tour_hotel_.tourcode = booking_record_.tourrefcode Inner Join explorer.hotelrecord hotelrecord_ On tour_hotel_.hotelcode = hotelrecord_.hotelref Where booking_record_.bookingdate Not Like '0000-00-00' And booking_record_.tourdeparturedate Not Like '0000-00-00' And hotelrecord_.hotelgroup = "LPL" And Year(booking_record_.tourdeparturedate) Between Year(AddDate(Now(), Interval -5 Year)) And Year(Now()) My MySQL skills are certainly not up to scratch, the actual result set I wish to find is "a customer who has been to 5 or more LPL hotels in the past 5 years". So far I havent got as far as dealing with the count as I'm getting a huge number of results with some 250+ per customer. I assume this is to do with the way I'm joining tables. Schema wise the booking_record table contains a tour reference code, which links to tour_hotel which then contains a hotelcode which links to hotelrecord. This hotelrecord table contains the hotelgroup. The client table is joined to the booking_record via a booking reference and a client may have many bookings. If anyone could suggest a way for me to do this I'd be very grateful and hopefully learn enough to do it myself next time! I've been scratching my head over this one for a few hours now! Customers may have many bookings within booking_record Daniel.

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  • Passing in a lambda to a Where statement

    - by sonicblis
    I noticed today that if I do this: var items = context.items.Where(i => i.Property < 2); items = items.Where(i => i.Property > 4); Once I access the items var, it executes only the first line as the data call and then does the second call in memory. However, if I do this: var items = context.items.Where(i => i.Property < 2).Where(i => i.Property > 4); I get only one expression executed against the context that includes both where statements. I have a host of variables that I want to use to build the expression for the linq lambda, but their presence or absence changes the expression such that I'd have to have a rediculous number of conditionals to satisfy all cases. I thought I could just add the Where() statements as in my first example above, but that doesn't end up in a single expression that contains all of the criteria. Therefore, I'm trying to create just the lambda itself as such: //bogus syntax if (var1 == "something") var expression = Expression<Func<item, bool>>(i => i.Property == "Something); if (var2 == "somethingElse") expression = expression.Where(i => i.Property2 == "SomethingElse"); And then pass that in to the where of my context.Items to evaluate. A) is this right, and B) if so, how do you do it?

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  • LinqToSql: insert instead of update

    - by Christina Mayers
    I am stuck with this problems for a long time now. Everything I try to do is insert a row in my DB if it's new information - if not update the existing one. I've updated many entities in my life before - but what's wrong with this code is beyond me (probably something pretty basic) I guess I can't see the wood for the trees... private Models.databaseDataContext db = new Models.databaseDataContext(); internal void StoreInformations(IEnumerable<EntityType> iEnumerable) { foreach (EntityType item in iEnumerable) { EntityType type = db.EntityType.Where(t => t.Room == iEnumerable.Room).FirstOrDefault(); if (type == null) { db.EntityType.InsertOnSubmit(item); } else { cur.Date = item.Date; cur.LastUpdate = DateTime.Now(); cur.End = item.End; } } } internal void Save() { db.SubmitChanges(); }

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  • Django: Determining if a user has voted or not

    - by TheLizardKing
    I have a long list of links that I spit out using the below code, total votes, submitted by, the usual stuff but I am not 100% on how to determine if the currently logged in user has voted on a link or not. I know how to do this from within my view but do I need to alter my below view code or can I make use of the way templates work to determine it? I have read http://stackoverflow.com/questions/1528583/django-vote-up-down-method but I don't quite understand what's going on ( and don't need any ofjavascriptery). Models (snippet): class Link(models.Model): category = models.ForeignKey(Category, blank=False, default=1) user = models.ForeignKey(User) created = models.DateTimeField(auto_now_add=True) modified = models.DateTimeField(auto_now=True) url = models.URLField(max_length=1024, unique=True, verify_exists=True) name = models.CharField(max_length=512) def __unicode__(self): return u'%s (%s)' % (self.name, self.url) class Vote(models.Model): link = models.ForeignKey(Link) user = models.ForeignKey(User) created = models.DateTimeField(auto_now_add=True) def __unicode__(self): return u'%s vote for %s' % (self.user, self.link) Views (snippet): links = Link.objects.select_related().annotate(votes=Count('vote')).order_by('-created')

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