I have a sql query which is returning null value below is the section the iID is null.Once debugger reaches this it goes to exception as its result is NULL. How to control debugger from going to the exception.
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I am using an Access database to store (filepaths to) pictures as well as comments people can leave on them. One picture can have multiple comments, so the tables look like this:
_____________ _____________
|Photos | |Comments |
|------------| |-------------|
|Id (PK) | |Id (PK) |
|PhotoPath | |PhotoId (FK) |
|Description | |Comment |
|____________| |_____________|
What I need to do now is retrieve a list of all Photos along with their Comments. So I have a class Photo with a collection of Comments:
vb.net
Public Class Photo
Public Property Id As Integer
Public Property PhotoPath As String
Public Property Description As String
Public Property Comments As List(Of Comment) End Class Public Class Comment
Public Property Id As Integer
Public Property PhotoId As Integer
Public Property Comment As String
End Class
I can retrieve the records using an INNER JOIN query (right?), as such;
SELECT Photos.*, Comments.*
FROM (Photos INNER JOIN Comments ON Photos.Id = Comments.PhotoId)
From the result of that, for each row in the result I can create a new Photo instance, set its properties and put it in a List(Of Photo) for further processing (displaying). However, how do I handle the Comments? With this query I would get a lot of duplicate Photos. I'd get a row for each comment, but most of these rows will represent the same photos... How do I handle this the best way? I have used inner join queries before, but only for a one-to-one relationship so I never had this problem before. Now when I finally need a one-to-many relationship I realize I've no idea how to handle this appropriately...
There must be some standard way of handling this? When I previously handled cases like this I didn't use an inner join, I just retrieved all Photos first, then iterate through them and run another query to retrieve the Comments that belong to that Photo (SELECT * FROM Comments WHERE PhotoId = ?). That works fine, but when the tables are getting larger it is getting noticeably slower. So I want to do it in a single query, I definitely want to avoid running hundreds of queries if I can.
From r In ReceiptLines
Where
r.RECEIPT.RECEIPTDATE >= _reportStartDate
And r.RECEIPT.RECEIPTDATE <= _reportEndDate
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I am fetching all departments and their sales, average, count from the ReceiptLine, Receipt, ReceiptDiscount tables. The problem i am facing is, if i remove where discount > 0, I am getting null exception. But if I include that, then I only get sales that has discount. How would I write query that bring all sales less discount (if it has one).
how to take a query that returns a single row of data and load that data into textbox controls.I know about ExecuteScalar but it is only good for a single column of data from the query.
View 2 RepliesI have a bunch of tables who share the same kind of information, but each table has a different name for each. (There was no standardization on the naming scheme). Some tables have important data that others do not contain. Some tables that have shared important data, but they are null values. I'm writing a program to combine all the tables into one master table.
The problem is when I read in a field, the reader.getvalue(i) is null, and I cannot use that value to insert into my new master table, obviously. The null values are so random, and I cannot write IF THEN statements for every single field for every single table in the database. I'd have thousands of lines of code constantly checking for nulls, and then trying to figure out what to do with them. What can I do to convert these reader values from NULL into something VB/SQL can handle? ere is the code so you can get a picture of how I'm approaching this problem:
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I'm having trouble with a null result, when I compare the query it said I cant it give the following error "sequence contains no elements"
Dim existe = (
p In abc.Ventadetalles
Where p.idarticulo = txtArticulo.Text
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I am looping through the rows of a DataRowCollection and assigning the fields of each row to a variable. I always get "Input string was not in a correct format" no matter how I cast this. I just need gapCd to contain 0 if the field is null or the value otherwise. It seems the IsDbNull is not returning true properly. I've also tried DbNull.Value comparisons with no l
View 1 RepliesI have this simple-minded query:
select a.str_number+' '+a.str_name+' '+a.str_suffix+' '+a.str_apt AS addr from mytable
This query works as long as none of the concatenated values are not NULL. If any is null, the address does not show.
I tried this:
select IsNULL(a.str_number+' '+a.str_name+' '+a.str_suffix+' '+a.str_apt AS addr,'') from table
What I would like to accomplish is to replace NULL with empty space if the value is null but I still get no values.
I get a warning message that reads " Variable 'cust' is used before it has been assigned a value. A null reference exception could result at run time.", but it occurs in my vb file "Northwind.vb with the following code:
Public Class Northwind
Private cust As BizObjects1.Customer
Private Sub frmCustomer_Load( _
ByVal sender As System.Object, _
ByVal e As System.EventArgs) _
Handles MyBase.Load
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Warnings: Variable 'targetPath' is used before it has been assigned a value. A null reference exception could result at runtime.
View 39 RepliesCustomerStreamToRead' is used before it has been assigned a value. A null reference exception could result at runtime.I get that warning once I commented out the streamreader line listed below. The warning shows for the line loading settings(z). The app runs but I don't like warnings in my error list.
Code:
Public Sub LoadSettings()
Dim Z As Integer
Dim CustomerStreamToRead As StreamReader
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Background: I wrote code that will output all the currently logged in User's Active Directory group names. I want the group name (ex: Acomp_user_BIG) via IdentityReference.Translate instead of the current user's SID's (ex: S-1-5-32-544) returned via IdentityReference.Value.
Here is code that I used:
Public ReadOnly Property Groups As IdentityReferenceCollection
Get
Dim irc As IdentityReferenceCollection
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Due to this error I am getting a default date 1/1/1900. Variable 'dr' and 'dr1' is used before it has been assigned a value. Here's the code:-
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Variable 'loNode' is used before it has been assigned a value. A null reference exception could result at runtime.
why I am getting this error?
Imports System.Xml
Module Module1
Sub Main()
Dim doc As New XmlDocument
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I have the following code in my project:
rivate Sub Button1_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim connectionString As String
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I want to bind the following query result to datatable:
Dim query = From c in db.Customers _
Where c.Status = "Active" _
Select c.CId, c.FirstName, c.LastName, c.Email
First time poster and new to ASP programming.I have a functional database to where i am trying to add new functionality.I'm trying to add the idea to check if a returned string is empty, if so get value from a backup table which holds historical information. Here is what i have got for the specific part:
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I'm trying to run a query and display the result in a listbox. I can do it for a datagridview but not for a listbox .
Code:
Private Sub frmNieuweActie_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
strSql = "SELECT Acties.Actieid, Acties.Actie " & _
"FROM(Acties) " & _
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I get the correct amount of items in my listbox but it displays "System.Data.DataRowView" as item .
I am facing a problem displaying the result of my "select *" query on the form . Here is my code:
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But when I write this code and run my form I am not able to see any records present in my database tables being displayed on my form. I have inserted a DataGridView on my form . What changes should I do to my code ?
I'm trying to fill combobox with my SQL query result.[code]...
View 2 RepliesI am trying to fill a combobox using the results form a query to combine two fields (first and Last name). I cannot seam to get to the query through the table adapter. I can set the binding source and select one of the fields to fill the control but I cannot get to the query's.
View 2 RepliesHow do I assign the query result to a variable.I am using SQLlite. Below is the code for retrieving password from the User Table. I need to compare the given password and the given password.
Dim i As String
Dim p As String
i = txtUserID.Text
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I would like to parse the result of entering a query at [URL] the problem is that I cant seem to the post data just right and cant properly open a webrequest to the site.
View 3 RepliesI have added a query to my form using the sqlDataAdapter object and the wizard.Now I want to show the result of the query in a combox on my form.The combobox is not binded to a data source, but is going to be used for searching a record (but this is for later)
View 10 RepliesI am new in vb.net 2008.I want to populate items of a combobox with a result of a query that may include join or not.
View 3 RepliesI'm trying to show some concatenated data in a CheckedListBox so that users are able to select the data for use later on. Here is the code I am using currently:
Dim con As New MySqlConnection
Dim theQuery As New MySqlCommand
Dim theTables As New DataTable
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Is there a way to show the value retrieved by an SQL statement in a message box? In context, my SQL statement searches my database to find a customer record that matches the details entered into the text boxes on the form, and retrieves the CustomerID. Is there a way to show this CustomerID in a message box?
The SQL code is:
SELECT customerid
from customer
where cust_forename = @custforename and cust_surname = @custsurname and cust_house = @custhouse etc
I have a stored procedure:
CREATE PROCEDURE [TestProc]
AS
BEGIN
select '1a', '1b'
select '2a', '2b', '2c'
select '3a', '3b'
END
If I execute the following query using SQL Management Studio,
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How can I get the three result sets using SqlDataReader? Or even three SqlDataReader's? Or is it possible to get multiple result sets in just one query in VB.NET? Is DataSet my only option?
I have two text box(Start Value and End Value), one datagridview and a search button SQL script= Select id, ContactName from Customers where id between 1 and 5 I want a scenario where when I enter the start value 1 and end value 5 and click the search button it will run the above query and display the result in the datagrid view.
View 4 RepliesI'm looking to store the result of SQL count function in a variable, i've tried numerous ways but haven't managed to get it to work?
View 3 Replies