Sql Select Statement In Vb Returning Value When Its Supposed To Be Null?
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 & _
I am still a newbie with VB. If I return a number the if statement works fine, with opening the new form and updating it as needed. Id the if statement returns a Null from the database it crashes.
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]...
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.
Public Sub checkemail() sqlcheckemail = "select Email from WEBUSER where Email='" + TBEmail.Text + "'" Dim dscheckemail As New DataSet
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if u see the one that i've commented is the one i already googled at tested...so now if the email address exist in the db..everything works wonderful..but if it doesn't exist the code should process the one that does not satisfy the first if statement...but now i'm getting the result as "There is something" eventhough the email does not exist in the db...
This may seem like a dumb question, but how do you set a default date for the datetimepicker or set today's date as default in the table?
For some reason the control (every instance I've inserted so far) returns a null value when I try to update rows without selecting or entering a specific date while the program is running. The date columns are required, and in at least one case I need the date to automatically return today's date.
In the properties I have chosen "values" for today's date, past dates, even future dates, but I keep getting the following error:
A first chance exception of type 'System.Data.NoNullAllowedException' occurred in System.Data.dll
When I review the details, VS tells me that the date column in question does not allow nulls. If I select a date while running the program, I don't get this error, so it seems like the default value is not getting set.
I have this function correctly linked in an external .js file...
function SubmitAge(age, UpdatePanelID, HiddenAgeID) { $get(HiddenAgeID).value = age; __doPostBack(UpdatePanelID); }
and am calling it like this from an onClick of an a href="#" ... html tag (tags removed, please scroll right as stackoverflow has the greatest difficulty in displaying simple content, 7th display related edit,
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Why on earth is HiddenAgeId, clearly passed just like UpdatePanelID, is returning an "Undefined identifier Error"??? its perplexed me to the point where i have no room to move! have i missed something guys?edit: Update: turns out it works perfectly (as it should) when i load it up in FireFox, but has the resulting error in Internet Explorer, this is not a browser compatibility issue, it should also work in IE, but it doesn't!
I have this function correctly linked in an external .js file...
function SubmitAge(age, UpdatePanelID, HiddenAgeID) { $get(HiddenAgeID).value = age; __doPostBack(UpdatePanelID); }
and am calling it like this from an onClick of an a href="#" ... html tag (tags removed, please scroll right as stackoverflow has the greatest difficulty in displaying simple content, 7th display related edit, thanks stackoverflow)
a href="#" onclick="SubmitAge(24, 'ctl00_MainContent_arFrom_upAgeRange', 'MainContent_arFrom_HiddenAge')" runat="server" 24 /a
yet, i am getting this error, and its being called on the first line of the SubmitAge function (line with $get(HiddenAgeID)... etc...)
Error:Microsoft JScript runtime error: 'null' is null or not an object
i've copied and pasted my WATCH windows in visual studio .net (vs2010 beta 2 using vb.net & c#) while the execution breaks inside teh SubmitAge .js function...
age 53 Number UpdatePanelID "ctl00_MainContent_arTo_upAgeRange" String HiddenAgeID Undefined identifier Error
Why on earth is HiddenAgeId, clearly passed just like UpdatePanelID, is returning an "Undefined identifier Error"???
edit: Update: turns out it works perfectly (as it should) when i load it up in FireFox, but has the resulting error in Internet Explorer, this is not a browser compatibility issue, it should also work in IE, but it doesn't!
I am finding this weird issue. When I do this > activities.Where(Function(a) (Not a.IsDeleted And a.ParentId = 100) It returns an in-memory query & when I try opening it up, it throws a object not set exception. This only happens when there were no items which satisfied the condition. Shouldn't it be returning an empty set? When there are items satisfying the condition, then it returns a list & works all good.
In my VB.NET application when I try to get the image location using picturebox.ImageLocation (path), it is returning null. I have to use that path string in filestream's parameter to open it. Since it is returning null, I couldn't open the file (image) in filestream. The following error is coming: "Path cannot be null"
This is my code: Dim path As String = Picturebox1.ImageLocation Dim filestrm As FileStream = New FileStream(path, FileMode.Open) Dim arry(filestrm.Length - 1) As Byte filestrm.Read(arry, 0, filestrm.Length)
I want to put it (the select count statement) in this LINQ statement so I can get the sales count in my linq statement: Dim TheLeads = (From L In DB.Leads Where L.IsDeleted = False Select L).ToList() Is this possible to do in LINQ?
I am trying to call an external C++ function using VB.NET (answers in C# are fine, I can convert back) which returns a list of device names. This comes in the form of a pointer to a null-terminated array of null-terminated char arrays (correct me if I've misunderstood what I'm dealing with) with a function signature:
long GetNames(char*** names)
Most of the answers to similar questions I've found have involved something more like:
long GetNames(char** names, int length)
It appears from what I've read that I need to give it an IntPtr but I'm uncertain as to how this should be initialized, and in my case I don't know the length of the array. At the moment, in the VB module, I have:
<DllImport("MyExternal.dll", CallingConvention:=CallingConvention.Cdecl)> _ Function GetNames(ByRef names as IntPtr) As UInteger End Function
I've tried calling the function by passing an IntPtr initialized as IntPtr.Zero or using Marshall.AllocHGlobal, but I always get an AccessViolationException.
Any ideas on how I should be calling this function and how I get the return value into a managed string array would be greatly appreciated.
EDIT: I've found a sample function call in native C as follows:
I've just been burned again by the fact that there is no compiler warning when you fail to return a result in a Function that returns a Value type. I wrote the function:
Public Function CompareTo(ByVal other As MessageIndex) As Integer Implements System.IComparable(Of MessageIndex).CompareTo Me._messageIndex.CompareTo(other._messageIndex) End Function
which performs the CompareTo Function for two integers, then throws the result away and returns 0, because I forgot to either assign a value to CompareTo, or use Return, and that isn't flagged by the compiler because it's valid VB for a Value type.
I happen never to use "FunctionName = ReturnValue" because it hides information from maintenance programmers and also because I think it's insane .
Is there any way I can get the compiler to issue a warning whenever my Functions are missing a Return, whether it's a Value type or not?
Now that I've switched over to parameterized queries, everything is great except along with handling all the special characters that would otherwise disrupt an all text SQL stament, it's handling the word NULL. My code basically does this for every variable used in the entire SQL statement:
If strCallName = "" Then strCallName = "NULL" End If
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and that worked great for my old all text ones because leaving the word NULL out of single quotes would tell it yeah, that's actually null and pass it a true null value. Now with parameterized ones, it's literally passing it the word NULL I tried just leaving the string empty but then when I try to execute the command, it says that the parameter cannot be a zero length string. So how do you give a null value to a a parameterized query and make it actually send that to the database in the statement? Would strCallName = vbNull work or would it still say it's a zero length string?
I have a table which contains a list of products for a company. They input data about how much stock they have and also the level at which they want to be reminded that they need to order new stock.
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I want to list all the true results in a form which the user is then able to navigate through. What would be the best way to go about doing this?
I have the following query that I use to create a new record in a database. If I leave any field on the form blank, for example, it throws the error "Memo.Lastname" cannot be a zero length string. Other than that the query executes appropriately. Private Sub cmdSaveMemo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdSaveMemo.Click If Len(Me.txtMemoID.Text) <> 0 Then Memo.SaveMemo [Code] .....
In every date field I have, I cannot update it if it is null. For instance, I have the following query and it will throw an error if the date fields are Null or zero lengths. Any ideas? I try and parse and get the following error: String was not recognized as a valid DateTime. if i don't, it throws a null error.[code]
How can i return null values in if statement above. This statement is not working if condtion is false its retruning me 0 value even if condition is false
dim d as nullable(0f Decimal) d=(if(_dr("value") isnot dbnull.value,Convert.toDecimal((_dr("value")),Nothing)
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.
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.
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
with the following code which gets stucked on the line of reader = Cmd.ExecuteReader(). It says the SqlException was unhandled (An expression of non-boolean type specified in a context where a condition is expected, near '7/2/2010'.)
I have successfuly connected to a database and have create a select statement (with access) which works most of the time except when im trying to perform a where statement with a date:
strEmployeeDepartmentLocation = Application.StartupPath con.ConnectionString = "PROVIDER=Microsoft.Jet.OLEDB.4.0;Data Source = " & strEmployeeDepartmentLocation & "swineFlu.mdb" strSQLSelectQuery2 = "SELECT NumberOfCase FROM table1 WHERE Date = 21/04/2009;"
i dont no if im writing it in the wrong format or what but it dont seem to bring back any data
