Referencing Data In DataTables Using Composite Primary Keys?
Apr 25, 2012
i have a project where I need to concatenate strings from 4 different tables based on a sequence of numbers. I created a 5th table that holds the number sequence and dictates in what order the strings get appended. I have created primary keys on the tables, but 3 of the tables are composite primary keys. I have written up to where I start referencing the primary keys, but am not sure how I should reference the keys on the actual tables. I saw some examples for creating composite keys from an array which I did. The main questions are did I declare the composite keys correctly, am I creating the composite key reference from the array correctly, and how should I reference it all to append to the stringbuilder variable.
[Code]...
And yes I kn ow it would be easier if I used Strongly Typed Dataset, but this is a clr sql stored procedure and have not found any examples on how to add a .XSD to a stored procedure. The add item option is not available, besides a bunch of typing
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Aug 23, 2011
On a client i have an anonymous list containing a multi-column primary key previously selected from the DB.Then i need to select all the records from the DB that equals the primary key list i have stored in the memory.[code]
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Jan 10, 2011
SELECT
T.TABLE_NAME as TableName,
T.CONSTRAINT_NAME as CONSTRAINT_NAME,
K.COLUMN_NAME as FieldName,
K.ORDINAL_POSITION
FROM
INFORMATION_SCHEMA.TABLE_CONSTRAINTS T
INNER JOIN
INFORMATION_SCHEMA.KEY_COLUMN_USAGE K
ON T.CONSTRAINT_NAME = K.CONSTRAINT_NAME
WHERE
T.CONSTRAINT_TYPE = 'PRIMARY KEY'
AND T.TABLE_NAME = 'mytable'
ORDER BY
T.TABLE_NAME,
K.ORDINAL_POSITION
Query for getting pk of a table. When I Run this query to fill dataset from dataadapter it does not return any value while it returns a row when executed from sql server. Fill method is called correctly as it is working from past 8 months and no problem is yet is there any special property of dataadapter. I also used to put above query in a sp and when try to execute that sp the result was sq not found.
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Apr 2, 2012
EDIT: was a design issueI am undergoing a computing project for Alevel computing.The project consists of a 6 tabled Microsoft access database. I am using vb.net to code the application for a student tracking system.My ERD is below:My problem: How to insert a new compound Primary key into a existing table?If I increment StudID and CourseID in tblContact then I need to increment them in tblStudentCourse which leads to records not pointing to the right directions..For enforcing the relationships I am using the .relations with the dataset.
'Student - StudentCourse
DS.Relations.Add(New DataRelation("StudStudCorRelation", DTStudents.Columns("StudID"), DTStudentCourses.Columns("StudID"), True))
[code].....
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Oct 28, 2008
anyone know how sql pick a random number of primary keys, I know get max number and call a random number work but what if there a missing numbers like 1,2,4,6,7 so max 5 and random will missing 6 and 7 also there a error if 3 and 5 come up.
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May 7, 2011
What is the best way to manually generate Primary Keys in Entity Framework 4.1 Code First?
I am programming ASP.NET MVC 3 and I use a repository pattern.
I currently generate keys in a sequential order by using the [code]....
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Oct 5, 2009
I had a post about how to disable monitors, but someone suggested just making it not possible to leave the primary screen. This was obviously a good suggestion, but im not sure how i would accomplish this.
I need to prevent the user from entering the ctrl, alt, delete, escape, and windows key. I also need to prevent the mouse from leaving the primary screen.
My program is a security login system. It requires a username and password to close, and i want to make sure that it cannot close unless the user supplies the correct username and password.
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Feb 10, 2010
I have written a program which uses a SQL exception class and then use it show custom messages for the primary key violation. Also i want the primary key value that caused the violation. How can i get all the primary keys which generated the exception from the sqlexception object.[code]
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Jun 1, 2012
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]
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Jun 14, 2011
I have a sequence that reads the selected Excel-file and displays the first row of the columns in the Excel. (The first Excel row has the column names)
Dim cmd As OleDbCommand = New OleDbCommand("select * from [" & tableName & "$]", MyConnection)
Dim dr As System.Data.IDataReader
Dim dt As New System.Data.DataTable
dr = cmd.ExecuteReader
dt.Load(dr)
With the above code I can read the the first rows of the Excel table and choose the names of the columns I like to keep. (By populating the first row to my ComboBoxes)
So, at the moment my DataTable dt has all the table header names but on the first row. And as the header names it has F1, F2, F3, ... F13.
How can I make my new DataTable dt2 take the first row of dt and make it the column names row? How can I choose which columns do I want to transfer from dt to dt2 ???
I have tried the following (Doesn't work):
Dim dt2 As System.Data.DataTable
dt2 = dt.Copy.Columns("F1", "F2", "F3", "F4")
DataGridView1.DataSource = dt2
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Apr 27, 2009
The DataGridView Control only accepts one data source, but there are ways to brake through, ways that I'm not able to find.
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Mar 2, 2012
How i can import row from TABLE1 to TABLE2 without primary keyfield or adding correct value to primary key
i tried with two different codes, but result is same, it says: "In the column "Key"a constraint on the uniqueness.[code]...
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May 11, 2009
I am trying to match between two datasets. Based on some predefined criteria the matched items are stored into a datatable. I am using the code below: [code]I am not sure whether there are more effective way to store the matched items in a new datatable since the method I used here requires three loops which is a lot of processing time.
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Oct 2, 2011
I have the following code, which reads data from xml file and displays it in the datagridview. It all works fine:
[Code]...
Instead of showing read data in datagridview, i'd want to read the data from xml file into one dimensional array: X(Impedances) Or is there a way to read value from this datatable into string variable without getting data from datagridview? The point is: i'd want to scan through all "Impedance" values (which are read from xml file) and compare with value y to catch the nearest value to y. How to do that?
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Mar 4, 2010
Heres my issue, I am retrieving data from xml and populating a DataSet with the results into multiple DataTables but i have an issue where an item is repeated in my input data and it is causing it to exception because of the constraints imposed between these tables. how can i determine if a row exists prior to adding the DataRow and thus not include it in my DataTable?
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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]
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May 26, 2006
I want to be able to get some data from my database table, given the value of the primary key. This is what I have so far:
projectName = DbDataSet.Projects.FindByid(projectId).name
where projectName is a String, and DbDataSet is my dataset. The variable projectId is the ID of the row I want to extract the data from, but every time I run my code I get a NullReferenceException.
I know that the row with the primary key value of projectId exists because I can see it when I view through server explorer.
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Jun 2, 2009
I've got a couple of drop down lists for languages. I bind them to a language list that comes from a query. Then the fields are also bound to the row in the DB they relate to. I have several panels with the language drop down - each "tied" to a different table in my DB. When I call up different records on the same panel the drop downs immediately "set to the position" of that rows language in the list. But when I call up another panel - tied to another database table - I see that language in the drop down.
[Code]...
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Oct 21, 2008
I have a problem detecting whether one of the arrow keys is pressed, all the other keys seem to be detected apart from the arrow keys??? I have set key preview to True........ It detects the arrrow keys BUT ONLY if I have NO other controls on the form??? example..
Me.Text = e.keycode
It works, but then if I add a button for example, it stops.
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Nov 9, 2011
how to delete rows of data without using the primary key VB.netI am using Access 2003 & VB 2005
Private Sub BtnDel_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnDel.Click
Dim dt As New DataTable
[code]......
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May 26, 2009
I am new at asp.net, so I would be glad, if anybody could help me in this case... I scanned already the internet for answers, unfortunately with no success..I have a grid view, and this is loaded by a sql data table, this table has 2 keys (RezeptNr and Zutatnr). When I wanna update a row in the data grid, the RowUpdating event fires, so I need to read the Basket Session, what has the complete object stored. I put this in a DataTable (dt1), so far so good..The problem is line: Dim dr As System.Data.DataRow = dt1.Rows.Find(id) Here the compiler alerts, that I have two keys, and he cannot select the data sentence with the find method. I tried it with datatable.select command, that works, but then I have the data sentence in an array, but I need to update the data row of the data table.
[Code]...
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Nov 23, 2010
Basically the code below is supposed to load data from a reader into a datatable, then compare a date to the start date and end date in each row of the table.However, I am getting errors on the if statement indicating Overload resolution failed because no accessible '>=' can be called with these arguments.I can probably do this with just the reader but I am playing around with a data table because I know I will have to learn how to cycle through the records and look at them at some point and this is a simple example I can use to do this.[code]
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Apr 3, 2009
I have created a form that enables me to enter data for adding a new customer. so far i am able to save the data as a line and separte each field with a "#", with out any problem but the thing is i am not sure how to assin a primary key to the data, every time i add a new customer to my txt file i want the primary key to be one number higher than the previous.
so that i can l8r enter the primary key to search for the costumer and view that data
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Feb 3, 2012
How do I fetch the loginID and display the student data on the textbox?E.g. I login with loginID of 18 but it only display the data of 12
Private Sub frmLibrary_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'TODO: This line of code loads data into the 'LibraryDataSet.Student' table. You can move, or remove it, as needed.
Me.StudentTableAdapter.Fill(Me.LibraryDataSet.Student)
End Sub
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May 21, 2011
I have managed to successfully create a logon page and have created a form to insert data into one of my tables using text boxes and a "Save" button, however the first field in the table is the named "CustomerID" and is set to Autonumber, this is the primary key of the table. If I enter a record into the table in Access it automatically enters the next valid ID however when I can't seem to make this happen when entering data via my VB form!
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Dec 19, 2011
I would like someone to modify the following code to save data to generate the primary key for each record automatically. In the database,the ID column is the primary key and the Is Identity is set Yes.
Try
cmd = New SqlCommand("Insert into StudentDetails.programmes(ID,Programme,Form,AcademicYear,Class) values(@ID,@Programme,@Form,@AcademicYear,@Class)", cn)
cmd.Parameters.AddWithValue("@Programme", txtProgramme.Text)
cmd.Parameters.AddWithValue("@Form", txtForm.Text)
cmd.Parameters.AddWithValue("@AcademicYear", txtAcademicYear.Text)
cmd.Parameters.AddWithValue("@Class", txtClass.Text)
cmd.ExecuteNonQuery()
MessageBox.Show("Record successfully saved", "Saved", MessageBoxButtons.OK, MessageBoxIcon.Information)
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Dec 20, 2011
The primary key of the table is generated automatically using the Is Identity and I want to update based on the primary key. There is certainly something wrong with the following code, so I'd like someone to modify it for me.
Try
Dim qry As String
qry = "Update StudentDetails.Programmes set Programme=@Programme,Form=@Form,AcademicYear=@AcademicYear,Class=@Class where ID=ID"
cmd = New SqlCommand(qry, cn)
[code]....
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May 26, 2011
I defined a database using SQL Server 2008 R2 Express, and connected to it using Visual Basic 2010 Express. For some reason though, when I use the database in the program, it wants to start off using a negative primary key.Is there any way to make the primary key only a positive number?
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May 8, 2012
Create composite and custom grid control in ASP.Net 2008 or above
I need to create composite control . My control like one "div" inside that div one Gridview control.
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Jun 27, 2012
I'm trying to make a composite application.Lets say there are two regions with a view in each that interact with each other via drag and drop, view A contains a list of tasks that view b (which contains a list of People) doesn't really know about.When I select some tasks in the list from view a and drop it to another list maintained by view b which module should know what happened? does the module that maintains the tasks need to know about the module that maintains the people, or vice-versa? Where should I start?
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