基于SQL select语句的“对于每个”循环

Question

I am trying to figure out how to perform a 'For Each' loop for each distinct value returned from an SQL query.

Here is my pseudo code.

connection.ConnectionString = "server=***01\SQLEXPRESS; database=Billing; integrated security=yes"
command.Connection = connection
command.CommandType = CommandType.Text
command.CommandText = "SELECT DISTINCT [Customer] FROM [Billing]

For Each... Distinct value returned above

    command.CommandType = CommandType2.Text
    command.CommandText2 = "Select * FROM [Billing] WHERE [Customer] = [DISTINCT VALUE FROM ABOVE]
    dataAdapter.SelectCommand = command

        'Fill data to datatable
        connection.Open()
        dataAdapter.Fill(datatableMain)
        connection.Close()

Then Export (I am ok with the Export code)

In essence I need to be able to loop until I have a datatable per customer exported.

Hope that makes sense, any help greatly appreciated.

Answer 1

Here is some untested code. But it will give you a fair idea about what I was talking about (in the comments of question).

Sub Whatever()
    connection.ConnectionString = "server=***01\SQLEXPRESS; database=Billing; integrated security=yes"
    connection.Open()
    Using da As New SqlDataAdapter("Select * FROM [Billing] ORDER BY Customer", connection)
        da.Fill(datatableMain)
    End Using
    connection.Close()

    ' get distinct customers
    Dim dv As New DataView(datatableMain)
    Dim distinctCustomers As DataTable = dv.ToTable(True, "Customer")

    For Each customer As DataRow In distinctCustomers.Rows
        ' this messagebox is only to give you an idea which customer you are printing
        ' not required in actual code.
        MessageBox.Show("Exporting Customer... " & customer("Customer").ToString)

        Dim customerRows() As DataRow = datatableMain.Select("Customer=" & customer("Customer").ToString)  '<-- put single quotes around value if "Customer" field is of string type. e.g. "Customer='value'"
        For Each customerRow As DataRow In customerRows
            ' all the rows related to this customer are here
            ' do whatever you do to export

        Next
    Next
End Sub