Create A LINQ Query Statement That Retrieve Intersecting Data From 3 Datatables
Nov 26, 2010
I am trying to create a LINQ query statement that retrieve intersecting data from 3 datatables (dt, dt1, dt2). My first attempt to do so with the following LINQ query statement was successful: [code] However in my design, I would need the LINQ query statement to be dynamically generated, because I want a user to be able to retrieve intersecting data entries from VARIABLE number of datatables. In this case, the first option is not as good as the "INTERSECT" query operator, with which I can just easily connect each SQL query statement with a "INTERSECT" operator. The problem is that my second attempt using the "intersect" operator fails, and after many trials and errors I still can't get it to work. [code]
I'm having a hard time joining 2 datatables and have the joined datatable as result. First datatable (labels) holds data including a printerid. Second datatable (printers) holds printer references (id > unc). I would like to have as endresult (joined) a datatable with all data from the first datatable with the field (unc) of the second datatable. [Code]
Ok im trying to do a if statement in Linq and was wondering if it was possible to do something like:
Dim loadFriends = From p In db.UserRelationships Where p.aspnet_User.UserName = User.Identity.Name _ Or p.aspnet_User1.UserName = User.Identity.Name And p.Type = 1 _ Select New With {if p.aspnet_user1.user = "a certan username" then .username = _ p.aspnet_user.username else .username = p.aspnet_user1.Username}
We use LINQ to SQL extensively, and one of the biggest performance pitfalls we've run into is situations where a query can't be converted to SQL, and so an entire database table gets loaded into memory and the query performed by .NET. For example, this query
Dim Foo = (From c in Db.Contacts Select c Where c.ContactID=MyContactID) translates to a simple SQL query, whereas Dim Foo = (From c in Db.Contacts Select c Where c.ContactID=SafeInt(MyContactID))
doesn't because SafeInt is our own function and doesn't have a SQL equivalent; so the whole contacts table gets loaded into memory and searched by LINQ to objects, which is vastly slower. With a little experience, we've gotten better at avoiding this kind of situation. But it's not always obvious, and this is the sort of problem that's often not revealed until you're working with a lot of data and things start to slow down. Is there a straightforward way to see - whether in Visual Studio or some other way - how LINQ queries will be handled, other than trial and error?
am developing software using sql database. i want an sql statement that can enable me retrieve data which for example has same surname,save them in an array or dataset and navigate through them.
I have three tables in SQL server which I would like to show and access on a form. Table 1 contains account data, address, contact details etc. Table two contains data attached to a Person, tel no , Mobile no, Email etc. Table three contains details on what awards the person holds, i.e. one person can hold several awards.
Therefore I have a one many relationship between the first two tables and a one many relationship between the second two tables. This is set up in SQL
The first two tables are shown on a form, table 1 via a set of text boxes, table 2 via a datagrid control.
I would like the functionality whereby I could select a row in the datagrid showing the persons name and find the Persons_ID number then use that as a filter to a second datagrid view so that only the selected persons awards show in the datagrid.
I created a sql query to check if the mobile number is registered or not. If its registered, it will send the new pin code to the customer and if its not, the customer will get a message that "This number is not registered or you are not authorized to this"... something like that... Sending of new code is already working. I just dont know how to make it as conditional statement like PHP. After you query on PHP, you can just set a variable and make a conditional statement..Here is my script in vb.net:
Private Sub CheSMS() Dim SQLServer As String = My.Settings.SQLServer Dim conn As SqlConnection[code]......
In my programming task I've gone down a dark alley and wished I hadn't, but there is no turning back now.
I'm building up a SQL statement where the table name, column name and id value are retrieved from query string parameters i.e. ("SELECT [{0}] FROM [{1}] WHERE [Id] = {2};", c, t, id)
But it isn't as bad as it looks, I'm protected: Only authenticated users (i.e. signed in users) can execute the Page_Load I'm checking that both the table and the column exists beforehand (using GetSchema etc.)I'm checking that the Id is an integer beforehand All my tables have Id columns The database connection is reasonably secure
I had tried to use SQL statement to retrieve data record from SQL server, but when the database grow, the query speed getting slower. I just want to get most recent 5 records, any way to make it fast? Below is the SQL
i try to convert this kind of sql query into linq in visual basic, but i get stuck on how to make a percent.. I also don't know how to use linqpad for creating this linq
SELECT CASE RIGHT(PICName, 3) WHEN '(P)' THEN 'Problem' WHEN '(R)' THEN 'Request'
i created a database in my visual basic . and in this database i created 1 table...
i created also a query which is calculating the SUM of a colonm..i want to know how i can do to retrieve this data inside a textbox whos is on my program..ans of course i want that data to be update everytime i inserte data in this colonm...
I am tring to bind a data to listbox with where combobox.selectedvalue. My code is below; I am using data entity in wpf project;
Class Window1 Dim db As New AdvanceEntities Private Sub Window1_Loaded(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles MyBase.Loaded[code].....
Also I need to create a query with Join In statement. I need to get two table in one query, they have same values in USERID collumn.
I'm stumped trying to do an equivalent SQL statement in VB 2010 working with two DataTables, & am hoping someone could point me in the right dirction.I currently have two data tables with three fields each :- A, B, C. The data in field A is the same in both tables & could be used to join the two tables.How could I input data into a third data table having data from both primary tables ? Something along the lines of the following SQL code.[code]
I'm using a LinqDataSource to populate a basic GridView in ASP.NET. The user has the ability to filter the results, so I use a few WhereParameters and the Where within the LinqDataSource.My client has requested an option to export the filtered results to a file. Easy enough to pipe the data into a file, but I would prefer not to rewrite all the where clauses in the codebehind. I would simply like to extract the full set of results, preferably by using the already configure LinqDataSource.When using LinqDataSource's OnSelect method, the e.Result has the data I'm after, but my GridView PageSize is set to 20, which means that the LinqDataSource (rightly so) only fetches the first 20 records.Is there anyway to get hold of the entire data set?
I am using the following Select Statement to retrive data from my .csv file database:
Code: Dim comm As New OleDb.OleDbCommand("Select *, Left([Street Full Address], IIF(InStr(12,[Street Full Address],'-')>0, InStr([Street Full Address],'-')-1, Len([Street Full Address]))) as StreetFullAddress From " &
I am trying to retrieve information from one row that has four columns(name,company,address,phone) so that once it is displayed in 4 different textboxes, I can transfer to a word document.
I am using VB express 2008 with MS-Access as database.How i can retrieve data from a table having a column containing checkboxes on the base of Checkboxes checked or unchecked. Column PAID is having checkboxes.[code]...
I have to retrieve data in two TextBoxes but the data should belong to tokennum that I am getting from first text box. I have a total of three TextBoxes and one button. In a database called db1 I have a table named Table1 and two fields ser as serial number, tokennum for token number and name for name of employees.
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim con As New OleDb.OleDbConnection
And the following sub routine is load in the Listbox_selectedindexchanged event
CODE:
And listitem class
CODE:
And subsequently I want to Design the select query by adding the three column i.e. First Name, Middle Name and Last Name in the Listbox and by selecting the list item that will show in text box.
I've seen several posts on the subject, but none seem to answer this particular dilemma. I have two datatables that I obtained by querying two separate servers.[code]
I have three tables set up in a MySQL database called "event", "status" and "user". (as shown below:
EVENT TABLE (below) STATUS TABLE (below) USER TABLE (below)
and when I get data from the event table I use the SQL query statement below to bind the persons first and last names together as one variable called "name" and then bind that name to the respective user_id; and so on. However when I make changes to the event table it doesn't show the changes I've made. I'm certain it has something to do with the way I'm retrieving the data.
SELECT CONCAT(u.lastname, ', ', u.firstname) AS Name , s.message AS Message , DATE_FORMAT(e.timestamp,'%b %d %Y - %r') AS DateTime[code].....
I want to make a report with a query "Select * from StudMaster where StudID IN ('S0001','S0002','S0003')"For this I created a parameterised command object in data environment and set the query as:Select * from StudMaster where StudID IN ( ? )
Then I called in vb code as:Dataenvironment1.command1 ("'S0001','S0002','S0003'")
Is there anything wrong in it? It is not working..Plz help me out, how can I make it run.
I am stuck with an issue.I have two datatables, with the same table structure, i need to select data from table1 such that the records arent existing in table2is it possible to do this in vb.net? if yes then how?
I have two UNTYPED datatables: "Shelfs" and "Books". Data came from different databases.
I must create a "left join" relationship because I want a list of ALL shelfs and books (if they have any).
Dim dset As New DataSet dset.Tables.Add(dtShelfs) dset.Tables.Add(dtBooks)
[Code].....
I spent hours googling around, but all examples I found were only applicable to strongly typed dataSets, and how to build queries (not to get the data)
I could solve this the "easy" way: by looping both datatables and sending the rows to a third one, but I want to do this the "right" way and, of course... LINQ exists to make things easier and I don't know how to use it
I have been searching for quite a while about joining multiple datatables via LINQ to dataset (When i say multiple, i don't mean just 2!!!), and it seems there aren't lot of examples in the net. I have seen examples of joining two datatables, done that, no problem there. Now i want to join three datatables. And there's nothing i can find out there.For example i have a 3 datatables:
I know that LINQ queries are deferred and only executed when the query is enumerated, but I'm having trouble figuring out exactly when that happens.Certainly in a For Each loop, the query would be enumerated.What's the rule of thumb to follow? I don't want to accidentally enumerate over my query twice if it's a huge result.
For example, does System.Linq.Enumerable.First enumerate over the whole query? I ask for performance reasons. I want to pass a LINQ result set to an ASP.NET MVC view, and I also want to pass the First element separately. Enumerating over the results twice would be painful.It would be great to turn on some kind of flag that alerts me each time a LINQ query is enumerated. That way I could catch scenarios when I accidentally enumerate twice.
I am referencing a project so I can create a messaging system on my website. [URL] how I would replicate this function in my dal and bll so that I can get the same output. In the example they use a datacontext. I mostly return datatables in frim my DAL.
public List<MessageWithRecipient> GetMessagesByAccountID(Int32 AccountID, Int32 PageNumber, MessageFolders Folder) { List<MessageWithRecipient> result = new List<MessageWithRecipient>(); using(FisharooDataContext dc = conn.GetContext())
