Primary Key And Foreign Key - Reference Constraint
Apr 18, 2009
I just watched a video from Beth Messi about setting up a primary key and foreign key on a table.
I created two tables, one called customer and the other one called orders CustomerID is the primary key to the customer table OrderID is the primary ket to the orders table and CustomerID is foreign key to the orders table
Beth Messi said that this would maintain the integrity of the tables and she also mentioned something about setting up a cascade delete so that when we delete a record in the customer table, the customer's order in order table will get deleted as well.
how I can set up the cascade delete, Meanwhile, I tried deleting a customer record in customer table - a customer with orders, and I got the following error when I clicked save.
The DELETE statement conflicted with the REFERENCE constraint "FK_Orders_Customer". The conflict occurred in database "C:DOCUMENTS AND SETTINGSLOUISLOCAL SETTINGSAPPLICATION DATATEMPORARY PROJECTSWBINDEBUGTEST.MDF", table "dbo.Orders", column 'CustomerID'. The statement has been terminated.
Shall I use try catch to warn the user that the record that I tried to delete has an order? They can't delete the customer unless the orders table's record is deleted first?
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Jul 20, 2009
I am using a number of tables on my application and two of which have a foreign key constraint I have set between them. When I change the account number on the main table via a combo box all of the relevant information for that table on the form is updated accordingly. However, the child table which has a foreign key reference to the Account Number of the main table is not updated when the acocunt number is changed. I have set the update to cascade in the references but still am having issues.
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Mar 20, 2010
I'm developing an app in VB.Net (Visual Studio Express 2008, on Windows Vista) that connects to an Access relational database. The database has 3 related tables (TextSections, LineItems, Cycles) that I'm loading into my dataset. I've set up two foreign key constraints and want all changes to cascade through the related records in the child tables. I cannot get the cascades to reflect through.
For example, when I delete the parent record, the children records remain (in the database - they are removed from the dataset). Also, when I modify the parent record (change the Description field for example), the change is not reflected in the dataset datatable that holds the children records - unless I go through and ReLoad all of the data from the database and re-Set the constraints. I have set the .AcceptChanges, .UpdateRule, and .DeleteRule to cascade, and have also set EnforceConstraints on the dataset. Why aren't the changes cascading through the children?
Below I've pasted (1) the Load Routines for my datatables TextSections (parent), LineItems (child), and Cycles (child of LineItems); (2) the method that creates the constraints in the dataset, and (3) The Save routine for TextSections.
Friend Sub LoadTSTable()
Dim key(1) As DataColumn
Dim newCol As New DataColumn
[code].....
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Mar 1, 2012
I have an application that works with a database that uses foreign key constraints.
For example, we have an inventory table that has a foreign key constraint that references a table called case_names. If a user attempts to delete a case name that has any inventory items referencing it's ID, the action is restricted.
How can I display a message to the user that they will understand? 'You can not delete this case as it still contains inventory items.'
My thought is a try-catch (catching different error types?) but I do not really want to use this for something that may be expected.
The application is in VB.Net using MySQL.data
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Jun 15, 2011
myCommand = New SqlCommand(
"INSERT INTO tblBook(BookCode, BookTitle, Author, PublishingYear,
Price, EnterDate, CatID, RackID, Amount)
VALUES('" & txtBookCode.Text & "','" &
txtTitle.Text & "','" &
[Code]...
The INSERT statement conflicted with the FOREING KEY constraint "FK_tblBook_tblCategory". The conflict occurred in database "CIEDC", table "dbo.tblCategory", column 'CatID'. The statement has been terminated.
Was that because of my database's relationships?
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Nov 15, 2011
I am new to VB.net and have created a simple master detail windows form. I created a two table data set and then dropped the master table on the form as a continues form or a detail form with several text boxes to enter data. The child form is a data grid and was simple drag and drop from the data-set. All of this was done with drag and drop and I have added nor changed any code.test data that I have added directly to the database shows up with the proper parent child relationships on the form. I can also enter new records into the database using the parent only portion of my form. I can also update a child record.When I attempt to enter a complete record with data in both the parent form and the child data grid I get this error.
The INSERT statement conflicted with the FOREIGN KEY constraint FK_tblComplainant_tblUseOfForce. The conflict occurred in database "C:\SQLFILES\CCTS_2.MDF", table "dbo.tblUseOfForce", column 'UOFID'. The statement has
[code].....
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May 20, 2010
i am trying to write a code in which i need to perform a update but on primary keys how do i achieve it
i have written the following code: kindly look at it let me know where m wrong
[Code]...
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Apr 6, 2010
i am trying to write a code in which i need to perform a update but on primary keys how do i achieve iti have written the following code:
Protected Sub rgKMSLoc_UpdateCommand(ByVal source As Object, ByVal e As Telerik.Web.UI.GridCommandEventArgs) Handles rgKMSLoc.UpdateCommand
Try
KAYAReqConn.Open()
[code]....
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Oct 5, 2011
Is it possible to have a Foreign Key as the Primary Key?
<Key()>
Public Property AssignmentID() As Integer
<ForeignKey("AssignmentID")>
Public Overridable Property Assignment As Assignment
Public Overridable Property User As User
For the code above I get an error:One or more validation errors were detected during model generation:System.Data.Edm.EdmAssociationEnd: : Multiplicity is not valid in Role 'AssignmentLocks_Assignment_Source' in relationship 'AssignmentLocks_Assignment'. Because the Dependent Role refers to the key properties, the upper bound of the multiplicity of the Dependent Role must be �1�.
I'm trying to create a table which has one (or none) record per assignment.
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Jan 23, 2011
I'm having some major issues trying to figure out What's going wrong with my code.
The general problem is that I can't get the foreign key in one of my child tables to populate the primary key from the parent table. I have a parent table named "ISSUES" and a child table named "ISSDESC". The primary key for ISSUES is ISS_ID which is an autonumber. The foreign key is ISS_ID in the ISSDESC table which is just a number. I'm using MS Access and an OLEDBConnection as the method. I've created the relationship in MS Access and also created the datarelation in the VB.NET code.
I am able to submit the information into the database into the two tables but the foreign key isn't being populated therefore not being linked to the other table.
I think it's probably a very simple fix, but it's been eluding me for a good 8 hours or so. I am using a dataset and 2 data adapters, one for each table.
Code:
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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 13, 2009
I'm creating a program that uses sql statments to input data into a data base, but I'm having a problem with this error:The INSERT statement conflicted with the FOREIGN KEY constraint "FK_Job_ProductCode". The conflict occurred in database "FabList.mdf", table "dbo.ProductCode", column 'ProductID'. The statement has been terminated.
[Code]...
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Feb 21, 2010
While I've previously many years of relational databases and procedural languages, I'm stumbling with Visual Basic. In this problem, the simple situation is that I have two files, parent and child. The primary key of the parent file (Area file) is linked by a relation to one of the two fields that makes up the primary key in the child file (Project file) (unique key is formed from 'area' and 'project'). I have the default table adapters created on both files. I have created two maintenance forms showing one each of the two files in datagrid view format.I can create some records in the Parent (Area) file, but when I try to create a record in the child (Project) file, using one of the valid key values from the Area file, I get the 'ForeignKeyConstraint [relation name] requires the child key values [actual value] to exist in the parent table' which I'm absolutely definitely sure it does.
I haven't done any actual coding for those two maintenance forms, just dragged-and-dropped the files from the data sources screen onto separate forms so it creates the controls itself. But I can't work out, if it already knows the data does exist because I can load it back in to the Area maintence form, why it can't check itself to find out the record does exist. Why does it think the record from the parent record doesn't exist? It does exactly the same thing, whether or not the database is in access or SQL Server Express. I have all the latest updates.
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Jan 27, 2011
I have two function:
Public Sub AddData() Dim sSQL As String = "" Dim check As Boolean = Me.TestExistingRow("QUESTIONARIO1") If check = False Then sSQL = "INSERT INTO QUESTIONARIO1([USER]) VALUES ('" & Me.IdUser & "');" ExecuteNonQuery(Me.ConnString, CommandType.Text, sSQL) End If End Sub Public Function TestExistingRow(ByVal NameTable As String) As Boolean
[code]....
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Mar 1, 2011
im using try catch to handle this error uponm deletion of record that is foreign key to other table but it seems that my try catch is not working. im using asp.net (VB). can anyone help me???' i want to display an error message in my page.
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Jan 26, 2011
This is a follow-up to a previous question regarding locking on two List(Of T) objects. Suppose I have a function like this:
[code]...
which resides in a class that declares List1. In a multithreaded environment, I now understand that I should have a private locking object for List1 and lock List1 whenever it's modified or enumerated. My question is, should I do this:
[code]...
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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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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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Oct 23, 2009
I'm experiencing some weird behavior when trying to modify some DataTable objects. Upon the second call to the subroutine, I get the following error when I to copy the source DataTable to a working set:
System.Data.ConstraintException was
caught Message="Column 'pk' is
constrained to be unique. Value
[code].....
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Aug 6, 2009
I have a problem running a simple query: "select distinct payee from table". This query is set up in the dataset and is called GetAllPayee.My code goes something like:
Dim dtSources as new Datatable
dtSources =
Me.TblExpenseRecordsTableAdapter.GetAllPayee
Upon running I get the error:Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.The problem is, I haven't set ANY constraints on either the new datatable, or the dataset table (tblExpenseRecords). i.e. there is no primary key etc.
Can someone please help me out with this problem?I have no problems running the query through the wizard where I can view the results successfully.
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Jan 18, 2010
i just want to know if there is a way to implement constraint for parameters with a repeating pattern. For that i meant something like this
ParamArray pattern as Integer()
if i need an integer, and any amount of the "pattern" (the pattern here is one integer). so basically the pattern accepts 1 integer and multiples of 1 integer, meaning 2 integers, 3 integers so is there a way to upgrade this so we can have this pattern:
Integer, Boolean
and any valid combinations for this pattern will include
Integer, Boolean, Integer, Boolean
Integer, Boolean, Integer, Boolean, Integer, Boolean
etc, etc
currently the only way i can think of is to wrap Integer and Boolean as 1 object and apply pattern 1, but i was searching for a better alternative?
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Mar 28, 2009
I'm building an app that does calculations (in dollar amounts). I want to buildin a constraint that says the value entered into text box must be greater than 0. If the user does not follow this rule, I want them to get an error message.I have the calculations built and the error message, but not the constraint statement i.e. if users enter negative numbers the ouput is negative, which in the context of this app makes no sense. how a statement that would require the value entered into a text box to greater than a value.
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May 18, 2010
Im getting a constraint error when running the following code. there are four fields set as the primary key on the table: bid number, phase number, phase version, detail number.
It errors out saying that bidno, phaseno, phaseversion are the keys and unique. it does not mention the detail number, but it will error out as soon as i run the line dtDest = dsbid.phasedetail.copy....or, if i use the clone (as in the example below), it errors as soon as i add the row.
CODE:
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Aug 26, 2010
I have a datagridview in which the user can add new rows. The datasource is a datatable who has a unique-constraint for the column "Position". Thus, if the user enters a position already existing, an exception is thrown. To avoid the ugly standard error message, I simply handle the dataerror-event and set e.cancel = true. This works. But if the user presses escape, the row_validated-event is triggered. I use this event to format the rows containing new data by changing the font color to red. Here another exception is thrown (SystemOutOfRange-Exception) telling me that the index xxx has no value. How can I achieve row-formatting for new/modified entries without getting this error?
Here is my code:
''' <summary>
''' Catch exception and cancel illegal action.
''' </summary>
''' <param name="sender"></param>
''' <param name="e"></param>
[Code] .....
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Mar 22, 2012
i'm using a strongly-typed dataset and i created a table adapter with a query and i previewed the data and it works fine but when i run the application it can't fill the table with this query and it throws an exception that it violates a constraint orkeyFailed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.
System.Data.ConstraintException was unhandled
Message=Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.
[code].....
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Apr 29, 2010
I was creating an XML Schema from a project 2003 XML. All was fine until I rebooted the machine and tried to re-open the file. I am now getting an error along the lines of:
"Identity Constraint not declared".
I've compressed and attached the file.
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Jan 26, 2010
In asp.net 2.0 I have several "dropdowns" defined using generics (examples eye color, hair color, etc). The fields are all typical; id, text, etc. All are defined as their own classes which must implement an interface I created called ILookup. However, when I try to return a List<> of this class using:[code]
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Jun 10, 2009
I have a problem that adding a new ROW with duplicate UNIQUE id throws CONSTRAINTException that I cannot always catch.. Randomly general exception halts my VB software, sometimes catching works. here is my code.
[Code]...
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Jan 8, 2011
In vb.net, it is possible to design a function which can operate on generic parameters which meet multiple constraints. For example, it is possible to have a function accept as a parameter a class which inherits from Control and implements IList. This function could use "Control" or "IList" methods on such an object, and also pass the object to anything that expected a Control or an IList [note that this particular combination was chosen to facilitate a brief example, not to be a particularly useful combination].
[Code]...
This approach provides compile-time type-safety; there's no need for a cast that could fail at runtime. An alternative approach would be to pass the argument as either a Control or an IList, and have the function cast to the other. That would, however, fail at runtime if the object that was passed didn't in fact meet both constraints.
Under what circumstances is it good to use a generic function like the above, in what cases would it be better to have objects which are going to meet both constraints have a new interface like IListableControl(Of T) which would include a TheControl property that would return itself (cast as a control), and in what cases would it be better to have a generic ISelf(of T) interface, any implementor of which would be expected to provide a "Self" property that would return itself as a T?
Using multi-constrained generics, it's possible to do a lot of things without requiring any run-time typecasts, but I don't know what the performance costs are likely to be. I tried writing a short program to generate 65,536 different generic types at run-time, e.g. Foo(of Bar(Of Foo(Of Foo(Of Bar(Of Foo(...(Of Blah)) and it got pretty slow, so I can tell that the time required to handle generics isn't fixed, but I don't know what factors affect it.
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Jul 22, 2011
I've got this Function:
Public Class QueryStringUtil
Public Shared Function GetQueryStringValue(Of T As Structure)(ByVal queryStringVariable As String) As T
Dim queryStringObject As Nullable(Of T) = Nothing
If queryStringVariable <> Nothing Then
If HttpContext.Current.Request.QueryString(queryStringVariable) IsNot Nothing Then
queryStringObject = CTypeDynamic(Of T)(queryStringVariable)
End If
End If
Return queryStringObject
End Function
End Class
When I try to call it like this:
Dim intTest As Integer = QueryStringUtil.GetQueryStringValue(Of Integer)("stuff")
Dim stringTest As String = QueryStringUtil.GetQueryStringValue(Of String)("stuff")
Dim datetimeTest As DateTime = QueryStringUtil.GetQueryStringValue(Of DateTime)("stuff")
stringTest gives me the error:
'String' does not satisfy the 'Structure' constraint for type parameter 'T'.
I want our other developers to not worry about having to convert a class to a structure or some stuff like that when they call this function. I just want them to be able to put a standard type in the (Of T) and have it work. I don't mind writing in extra calculations to achieve that. The other problem is I also need the function to be able to return an actual null value, so I kind of need the queryStringObject as Nullable(Of T). Which means I have to have T as Structure otherwise it tells me that won't work. So looks like if I change what T is I need to run some calculation to delcare the var as nullable or not.
I tried overloading this method so that one returns T and one returns Nullable(Of T) like so:
Public Shared Function GetQueryStringValue(Of T As Class)(ByVal queryStringVariable As String) As T
Public Shared Function GetQueryStringValue(Of T As Structure)(ByVal queryStringVariable As String) As Nullable(Of T)
And naturally it's telling me it can't do that since they just differ by return types. Is there anyway to overload this? I really don't want to have two functions.
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