Aggregate Data Functions in Disconnected DataSet

[Guest]

H
Is there an easy way of performing the "SELECT Count(columnname), columnname from tablename" database command on a disconnected DataSet to enable me to display a chart of numbers of distinct values, which will vary, in a Windows form

Many thank
djm

 

[Cor]

Hi djm.

Only one answer, No, you have to do a Select distinct of the database for
that.

Or make an itterating routine, not that difficult of course.
I made once a generic sample of it, but I do not know if it real fits your
problem?

You have to test it yourself, I am not sure if I did that completly.

Cor


\\\
Me.DataGrid1.DataSource = mydistinct.distinct(dt, "elem1")


End Class
Public Class Selectclass
Public Function distinct(ByVal dt As DataTable, _
ByVal dist As String) As DataTable
Dim dtclone As DataTable = dt.Clone
Dim dv As New DataView(dt)
dv.Sort = dist
Dim myselold As String = ""
For i As Integer = 0 To dv.Count - 1
If myselold <> dv(i)(dist).ToString Then
Dim drn As DataRow = dtclone.NewRow
For y As Integer = 0 To dv.Count - 1
drn(y) = dv(i)(y)
Next
myselold = dv(i)(dist).ToString
dtclone.Rows.Add(drn)
End If
Next
Return dtclone
End Function
End Class
///

 

[Jay B. Harlow [MVP - Outlook]]

djm,
If all the data you want is in tablename in your DataSet, you can use
DataTable.Compute to find the count.

Dim ds As DataSet
Dim table As DataTable = ds.Tables("tablename")
Dim count As Integer
count = CInt(table.Compute("Count(columnname)", Nothing))

For allowed aggregate functions see the DataColumn.Expression property in
the online help.

Note you will need to use seperate DataTable.Compute calls for each column
you want a count of, alternatively you could "roll your own" loop as Cor
showed and compute all columns in one iteration.

Hope this helps
Jay

Hi
Is there an easy way of performing the "SELECT Count(columnname),

columnname from tablename" database command on a disconnected DataSet to
enable me to display a chart of numbers of distinct values, which will vary,
in a Windows form?