Lets say I have a dataset with I dunno 20 records in it.
How do I get to the 16th record in the dataset or the Nth? So any number from 1 to 20
I have spent most of this week trying to think of a method and so far I have gotten no where.
I want the 16th record down in this dataset and there doesn't seem to be a specific command for it.
I'm working in VB.NET with OLE commands.
I'm not sure any code would be of any use to help solve this but I'm populating the dataset something like this:
SQL_Str = "SELECT FROM A TABLE WHERE CRITERIA IS MET"
dbDataAdapter = New OleDbDataAdapter(SQL_Str, dbConnector)
dbDataAdapter.Fill(DataSet, "SelectedRecords")
Now what do I do to get to the 16th row in this dataset knowing that there is 20 records in the dataset?
Since you say you are using VB.NET, just read the row from the dataSet.
Private Function GetRow(ByVal ds As Data.DataSet, ByVal rowNum As Integer) As Data.DataRow
Dim result As Data.DataRow = Nothing
Dim table As Data.DataTable = ds.Tables(0)
result = table.Rows(rowNum)
Return result
End Function
There are overloads to DataSet.Tables: Consider:
Related
I have table that needs to contain 50 columns for each half hour in the day (+2 for daylight savings). So each column will be HH1, HH2, HH3... HH50.
I have written this piece of code in the report properties code section.
Function GetHH() As List(Of String)
Dim headers As List(Of String) = new List(Of String)
For index As Integer = 1 to 50
headers.Add("HH" & index)
Next
return headers
End Function
Is there a way to use the output of this function as the headers of my tablix? Or will I need to add the headers to some sort of dataset in the database and add it from there?
The column group functionality would be well suited for this. As you mentioned, you would need to write a SQL statement to return these values in a dataset. Then you can set your column group to group on these values. This way your table always gets the right number of columns and you don't have to add them manually.
I am trying to pass a query and existing datatable into a function. The function will query the passed datatable using the passed query and return the result.
Unfortunately, I am unable to return any data. I have posted my code below. Can anyone help me fix it? I don't know what I am doing wrong.
Public Function ExecQueryTest(Query As String, DT As DataTable) As DataTable
Dim Result() As DataRow
'initialize the table to have the same number of columns of the table that is passed into the function
Dim LocalTable As DataTable = DT
'initialize counting variables
Dim x, y As Integer
'use the select command to run a query and store the results in an array
Result = DT.Select(Query)
'remove all items from the localtable after initial formatting
For x = 0 To LocalTable.Rows.Count - 1
LocalTable.Rows.RemoveAt(0)
Next
'for loop to iterate for the amount of rows stored in result
For x = 0 To Result.GetUpperBound(0)
'add each array row into the table
LocalTable.Rows.Add(Result(x))
Next
ExecQueryTest = LocalTable
End Function
If there is a better way to accomplish my goal, I don't mind starting from scratch. I just want to be able to handle dynamic tables, queries, and be able to return the information in a datatable format.
The problem is here:
Dim LocalTable As DataTable = DT
That code does not do what you think it does. DataTable is a reference type, which means assigning DT to the LocalTable variable only assigns a reference to the same object. No new table is created, and nothing is copied. Therefore, this later code also clears out the original table:
'remove all items from the localtable after initial formatting
For x = 0 To LocalTable.Rows.Count - 1
LocalTable.Rows.RemoveAt(0)
Next
Try this instead:
Public Function ExecQueryTest(Query As String, DT As DataTable) As DataTable
ExecQueryTest = New DataTable() 'create new DataTable object to hold results
For Each row As DataRow In DT.Select(Query)
ExecQueryTest.LoadDataRow(row.ItemArray, True)
Next
End Function
Though you may also need to clone each DataRow record.
You can clear a table with just
LocalTable.Clear()
instead of using that cycle, Also the results of your select can be directly converted to datatable using
LocalTable = Result.CopyToDataTable
Can you tell me how to get ages from 0-5 and so on from sql server and input the total in a textbox or label? please click the link for sample
Generate Ages
thank you!
Do you mean something like
Dim sql As String = "SELECT age_column FROM your_table WHERE age_column BETWEEN '0' AND '5'"
'The above line selects the all records where age is between 0-5 (Change the variables)
Dim da As New OleDbDataAdapter(sql, connectionstring)
Dim ds As New DataSet
Dim dt as new DataTable
da.Fill(ds)
dt = ds.Tables(0).Copy()
' Above code stores the results in an iterable table
Dim i As Integer = 0
For Each dr as DataRow in dt.Rows
i = i + 1
Next
TextBox1.Text = i
'i will be the total number of records where age is between 0-5, and display it in a `TextBox`
Your question is, however, very poor, and normally people would not put too much effort into answering it, since you've put no effort in yourself.
I hope this is a simple question and you don't have to waste too much of you time on it.
I have an report (called repRAD78) which contains a textbox (called txtRAD8). I would like to populate txtRAD8 with a calculated value based on numbers pulled from a query called qryrRAD78.
Looking through the forums it looks like recordsets would be the solution but this is my first foray into recordsets and it's not going well. :(
The code I have pasted in below I have pulled together from a number of places and it doesn't produce any errors but puts the same value into txtRAD8 for all the records.
I'm sorry if this is a stupid question but it's been driving me potty.
Many thanks for your time.
Al.
Public Sub Calc()
Dim dbs As DAO.Database
Dim rst As DAO.Recordset
Set dbs = CurrentDb
Set rst = dbs.OpenRecordset("qryrRAD78")
rst.MoveFirst
Do Until rst.EOF = True
Dim lngMean As Long
Dim lngRAD78max As Long
Dim lngRAD78_1 As Long
Dim lngRAD78_2 As Long
Dim lngRAD78_3 As Long
Dim lngRAD7 As Long
Dim lngRAD8 As Long
lngRAD78_1 = rst![RAD78_1]
lngRAD78_2 = rst![RAD78_2]
lngRAD78_3 = rst![RAD78_3]
lngRAD8b_c = rst![RAD8b_c]
lngMean = (lngRAD78_1 + lngRAD78_2 + lngRAD78_3) / 3
lngRAD78max = Maximum(Abs(lngRAD78_1), Abs(lngRAD78_2), Abs(lngRAD78_3))
lngRAD7 = ((lngRAD78max - lngMean) / lngMean) * 100
lngRAD8 = ((lngMean - lngRAD8b_c) / lngRAD8b_c) * 100
txtRAD8.Value = lngRAD8
rst.MoveNext
Loop
rst.Close
dbs.Close
End Sub
Private Sub Detail_Format(Cancel As Integer, FormatCount As Integer)
Calc
End Sub
Here's a second approach to this. Rather than using a function in the code, take the calculations from your Calc() routine and put them in another query.
SELECT idrRAD78,
(RAD78_1 + RAD78_2 + RAD78_3) AS Mean,
(IIf(Abs(RAD78_1) > Abs(RAD78_2),
IIf(Abs(RAD78_1) > Abs(RAD78_3), RAD78_1, RAD78_3),
IIf(Abs(RAD78_2) > Abs(RAD78_3), RAD78_2, RAD78_3))) AS RAD78Max,
(((RAD78max - Mean) / Mean) * 100) AS RAD7,
(((Mean - RAD8b_c) / RAD8b_c) * 100) AS RAD8
FROM qryrRAD78
This will give you a query that performs the same calculations as your existing function. Then just edit the report query to join to this new query (just like joining a table) using something like:
FROM ReportQuery INNER JOIN NewQuery ON ReportQuery.idrRAD78 = NewQuery.idrRAD78
Change the query names to match the real names. Add the fields from the new query in the SELECT part of your report query:
SELECT <existing field list>, RAD7, RAD8
Then set txtRAD8 to the RAD8 field.
I'm just doing this from memory as I'm not in front of my own computer, but hopefully that makes sense and is close enough to the correct code.
The problem with this function is that every row on the report is going to have a textbox called txtRAD8. So what you are really doing is updating every textbox on the report with the same value (once for every loop through the recordset). You are not actually setting the value for each individual row.
What you need to do is make the value of the textbox = Calc(RowID). Then your query uses the passed-in parameter to get the value for that one record instead of looping through the whole recordset, and updates just that one row on the report.
So your Sub becomes a Function, and returns the calculated value.
I am developing a program for a chain of restaurants, they should normally be able to calculate their guestcount and sales through a vb.net application with a connection to dbf files.
My dataset gets filled in correctly as is my datatable (checked by filling in datarowview = right data)
But then I get a problem, in all my functions using my datatable, the datatable skips the final value, in this case it is all values from a month so it either skips 31 or day 30.
Tried while, Tried for each, debugged alot (how i found it was the last value). But now I have no idea why the last value isn't used by the function
Public Function Getgctakeout(ByVal i_table As DataTable)
table = i_table
i = 0
gctakeout = 0
For Each row As DataRow In i_table.Rows
gctakeout = gctakeout + Convert.ToDouble(row(4))
Next row
'MessageBox.Show(gctakeout)
Return gctakeout
End Function
This function does not use the value of the last row to calculate gctakeout
what in the name of the lord is wrong :)
Assuming that your DataTable is really filled correctly, you have two other options to get the sum.
Use the old DataTable.Compute method which works also with .NET < 2.0
Use Linq-To-DatSet and it's Enumerable.Sum
1)
Dim Sum = CType(table.Compute("Sum(ColumnName)", Nothing), Double)
2)
Dim Sum = table.AsEnumerable().
Sum(Function(row)row.Field(Of Double)("ColumnName"))