VS 2010 SQL Select With Null Value?
Jan 28, 2012
I want to select all records in a table and only 1 field in 2 related tables so my query is:
strSQL = "SELECT CL.Name, CL.FirstName, T1.Description, T2.Description " & _
" FROM Clients CL, Table1 T1, Table2 T2 " & _
" WHERE CL.Tab1Cod = T1.Code " & _
" AND CL.Tab2Cod = T2.Code"
All works and all records are selected only if fields CL.Tab1Cod and CL.Tab2Cod contain data but if one or both contain NULL value then NO record are selected. how can I test in a query statement if a filed contains a null value and, in this case do not expose the related field ?For example if CL.Tab2Cod is null the field T2.Description will be empty but all other fields are exposed.
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Feb 16, 2011
Having trouble importing a value from a .csv file to a .csv file. This this done because data needs to be massaged and the data file renamed. This is a user interface. Do not want to have the user touch the .csv in any way except upload to the application so the applicaiton can do manipulation. Either way here is the issue.
There is a column in the original .csv file that contains a zip code. The first row of the .csv has a value of 17003 in the zip code column. In the second row of the .csv the zip code column has a value of 11746-9984. The value in the zip code column from the second row always comes back as a Null value. My guess is that the OleDbDataAdapter is defining some kind of Schema. Again, the first row containing the zip code column probably insists the value must be numeric. When the data table field is established it probably gets defined as numeric. If that is true and the second row of the .csv zip code column is not numeric that must cause the zip code value to be Null.[code]...
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Jan 25, 2012
I've got a table that caches calculated values for certain dates. I want to use LINQ to select all rows where the calculated value fields are null.But when I use isNothing I get an error that LINQ can't translate this into T-SQL. Is there a way to select null values with link, like this...?
Dim var = From rec As Record In myDataContext.Records Where IsNothing(rec.calculatedValue) Select rec
Other posts on stackoverflow mostly discuss how to avoid or check for null values with LINQ.
Note: I can't just set cacluatedValue's default to -1 to flag records whose calculated value has not been set (and then select those records) because I run queries that sum/average the calculated values. Selecting nulls seems cleaner and less bug-prone.
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Apr 3, 2012
My code seems to behave a way I don't understand. Sometimes it returns null as expected and sometimes it returns a value when its supposed to be null. How can someone explain this? Here is the code that selects from access and displays the result in a messagebox:
cmd5.Connection = cnn
cmd5.CommandText = "SELECT receipt_num " & _
"FROM brought_coffee, farmer where crop_year= " & yr & " and " & _
"brought_date=#" & dtt & "# and farmer_centre='" & ctr & _
[code]....
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Mar 29, 2010
I'm trying to use a select case statement to evaluate the value being passed from an array list...any suggegstions. I need to determine if the array is null or not, and setup my select case statement based on if the array is populated. See sample code below Code Sample selected As New ArrayList
Dim dvExisting as DataView
Dim grdExisting as DataGrid
For
i = 0 To dvExisting.Count - 1
If grdExisting.IsSelected(i) Then
[Code]...
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May 29, 2012
Not sure what I am doing wrong, but here is the code.
SQL Server Express 2008 R2
VB 2010
Private Sub FillDataSetAndViewGrid()
[Code].....
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Nov 9, 2011
I 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.
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Feb 2, 2011
I'd like to take all suggestion either in C# or VB.NET.I have a DB diagram like the image below. I also include the database script here [URL]In the Students table, CountryId and RoomId column are allowed null. Because some records do not have info about room and country yet.Also, some students do not have essays.I'm doing a joint query with all tables. I want to select all students to project the result like this:Wanted query result.
Here's my current query that gives the result like the image below:
Dim db As New DBDataContext
Dim query = From st In db.Students _
Join c In db.Countries On c.Id Equals st.Id _
Join r In db.Rooms On r.Id Equals st.RoomId _
[code].....
current query result I got only one result back because I have (2) William NoMan record in every table. But I don't get anything about others, like (3) Sync Master who has everything but RoomId.What do I need to modify the query above so it will give me all students like in the wanted query image above?
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Mar 29, 2011
i am trying to auto select the email value from a 2nd cbobox when the user selects a name from the first cbobox using the first cbobox's index. (the values all line up with each other just fine)This is my current code:
Private Sub cmbAnalyst_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbAnalyst.SelectedIndexChanged
theAName = cmbAnalyst.Text
[code].....
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May 13, 2012
am developing a project and i am trying to use this code with my table which is under microsoft access 2010
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Dec 22, 2010
I typed this question once already, hit preview, and somehow never got the preview and lost what I typed. It has been that kind of a day.So here is my quick overview then I am going shopping. I am using OLE DB to select from an excel spreadsheet. It has over 15000 rows and 33 columns. Sometimes even when a cell is not null, it is returning a null value. If I just do a "select * where [termination date] is not null", for example, it will return no rows even though I can see with my own eyes that sometimes termination date is not null.
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May 27, 2012
y code below:
Function combobfill(ByVal table As String, ByVal field As String) As DataTable
addconnection.Open()
Dim selectstring As String = "select " + field.ToString() + " from " + table.ToString()
[code].....
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Jan 3, 2012
Straightforward question: I have a few variables that are doubles. I would like to be able to store a "null" state in them, i.e. I need to be able to represent that the variable doesn't contain valid data. I'd really rather not associate a boolean "is valid" variable with every single double
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Aug 23, 2011
I've done arrays before but,
For x = 1 To 5
Dim canvas(x) As ShapeContainer
Dim cell(x) As RectangleShape
[code].....
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Jun 30, 2011
im using this bit of code to recieve data from a database. problem is if one off the values in the databass is null it kicks up an error how can i handle this so in the event of a null value it gives a "" string value
[Code]...
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Nov 10, 2011
I'm confused at the variety of different ways to say "null" in VB.net. I've got text and numerical fields with checkboxes to mark unknown values; I just want to populate a table with the fields' values (if the corresponding checkbox is not checked) or null values (if checked) so I can later input them into a mySQL database.So my question is just which of the various null types I should be using in what situations.
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Feb 16, 2011
I am trying to pull data from a cell in the currently selected row in a DataGridView control. I fill the control with data from a SQL database through a dataset.I am trying to retrieve the index of the currently selected row so that I can pull the data out of the first cell in that row. Here is the code I currently have:
Dim i As Integer i = dgvSchedule.CurrentRow.Index MsgBox(dgvSchedule.Item(0, i).Value)Seems pretty simple to me, but for some reason I am receiving a "NullReferenceException, Object reference not set to an instance of an object" error on the second line.
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Apr 3, 2012
I just made a bunch of changes to my program, so I can't just undo what I did. My main form gives me the following error every time I try to load the designer:
Warning1Value cannot be null.
Parameter name: objectType
I have rebuild the project with no success. A few other posts have mentioned that there could possibly be a reference to a button or image that no longer exists, but I have no idea which one.
Also, I don't really know what the information below means, but it shows up on the error page under 'call stack', so I figured I would include it
at System.ComponentModel.TypeDescriptor.TypeDescriptionNode.GetRuntimeType(Type objectType)
at System.ComponentModel.TypeDescriptionProvider.GetRuntimeType(Type reflectionType)
[Code].....
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Dec 2, 2011
I'm having trouble figuring out what to do with the bolded part, when there are no nodes to return.If there are no image tags inside the <images> tag, i get an "Object reference is not set to an instance of an object".I have been searching and searching for an answer but can't find one.
Dim orders = From o In xmlLinq.Descendants("order")
Select New With { _
.orderID = o.Attribute("id").Value, _
[code].....
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Mar 14, 2011
This is related to my last question.Even though Access considers Nulls and zero-length strings (ZLS) separate values, often developers wish to treat them as equivalent for the sake of an If...Then statement or some other stretch of code. One way to accomplish this is to write code like this:
' Not so efficient
If IsNull(varAge) or varAge = "" Then
' do something
[code].....
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Feb 4, 2011
i keep getting this null reference exception error and i can't figure out what i need to do to fix it. I have this in the form
[Code]...
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Mar 18, 2012
keep getting this null reference exception error and i can't figure out what i need to do to fix it.I have this in the form
Private Sub cbLookUp_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cbLookUp.Click
Dim webDownload As New Net.WebClient
[code].....
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Jul 21, 2010
I've got a DataGridView that has a column that will show dates/times this column needs to be sortable so I use this to tell the DGV that it is storing Date type objects (so that sorting works fine automatically):[code]Now the problem is that there will be some records shown in this DGV that do not have a value for this date column. How can I display this? If I dont set a value for that column or I set it to Nothing then the cell just shows the minimum date value (01/01/1601).Oh and this DGV is not using data binding if that makes any difference. Perhaps this might be a good time for me to investigate this data binding lark though if that will help with this issue? I'm sure I recall seeing something about being able to use one value but display another value when you use data binding thats all.
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Feb 29, 2012
I have the following code that checks if the value in a cell contains a nummeric value.
Private Sub dgvOrderRegel_CellValidating(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellValidatingEventArgs) Handles dgvOrderRegel.CellValidating
Select Case e.ColumnIndex
Case 4 'Aantal
If Not IsNumeric(e.FormattedValue) Then
[Code]...
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Jun 16, 2009
.i'm having a slight problem with the following function i wrote
Dim bytes As Byte()
bytes = Convert.FromBase64String(Base64String)
However, it returns me System.OutOfMemoryException error when the Base64String contain large
[code]....
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Apr 18, 2011
I am reading dates from a table in a database to display in a DataGridView column that is formatted as a date. The problem is that when the value is null in the database my program errors out because it cant convert the value to a date. How do you guys handle this? *Edit: If I set the value of my date variable to "Nothing" it displays as "1/1/0001" in my DataGridView, and I would like the cell to be empty for the null dates.
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May 3, 2012
I've got a little problem. I'm trying to choose a background for the program based on Settings, but I'm getting a Null Reference Exception and I don't know what I'm doing wrong. Here's the
[Code]...
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Jun 11, 2011
[Code]...
By my logic, this should only assign .length to index IF the length of strItem is longer than 0. This check is there in case the listbox is empty, or the user has not selected an item. However, everytime I go through this code without an item selected I get:
[Code]...
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Jan 17, 2011
I'm using MySQL to store some numbers. One of the columns in the database is defined as unique, but it does allow multiple NULL-values. That is exactly how I want it.ut when I'm trying to load the data into my strongly typed DataSet, I get a error saying that a constraint fails... I do understand why that happens (several rows with NULL-values in a unique column), but is it a way to keep a DataColumn in vb.net unique, but still allow several rows with NULL-values like in MySQL?
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Jun 17, 2010
I'm receiving a byte array from a network device by using the TcpClient class and as I have no idea how much data will be being sent I have to just declare a buffer that is X number of bytes long and keep reading into that until I've got all of the data. I then convert this byte array to a string using Text.Encoding.ASCII.GetString but the problem is that this gets any null bytes that were at the end of the buffer after the string and it includes them in the string. This then means when I do String.EndsWith it doesnt work as I would expect it to because there are just loads of 0 bytes at the end of the string.
Once I had realised that was what was happening (which took a long time as these null bytes are completely invisible when you are looking at the data in String form) I thought fine I'll just use Trim on the string but I've found that this doesnt make any difference at all. I thought Trim was supposed to remove any blank space from the start/end of a string, which I assumed would include empty bytes as well.
So is there any alternative I can use that will trim the empty bytes off the end or do I have to do it the 'manual' way and loop through my byte array before converting it to string and remove any null bytes? One thing that has just popped into my head as I'm typing this is to try using the Chr method and pass it 0 and combine that with Trim like so:
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