Grouping in data table ( removing duplicates )

please excuse this thread is for / in connection with this thread

in a datatble, say for example table 3 columns
emp_id
emp_name
emp_class

here i don't want field emp_id to repeat for each row,
i mean i want to set empty value in the data table keeping only the first row entry
this check & update needs to be done for each emp_id.

i have done it by comparing each row with all the row and then setting the values to empty
very nasty & resource consuming & time consuming & harder to code

please some professional approach for this please.:wave:

If you setup the table with emp_id as the Primary Key, the database wont let you enter duplicate emp_id.

no no,
i am failed to visualize you, sorry

lets say 2 tables

table T1
emp_id (Pk)
emp_name
emp_class

table T2
emp_id (Fk)
Consumption
Consumption_date

now

Quote:

---

SELECT t1.emp_name,t2.consumption_date,t2.Consumption from t1 left join t2 on t1._emp_id = t2.emp_id group by t1.emp_id;

---

in the query above t1.emp_name will repeat redundantly, this i want to eliminate so as to retain only one emp_name for all his relative records
and then next emp_name & so on

this query will be loaded in to the dataset, further i need help please

What the ?....That shouldn't even be legal. SQL Server would never allow that as you need to aggregate non grouped fields. In such a case the name would not be repeated. I had no idea MySql allows that abomination....but then again, what do I know. I'm curious to see what the guys more experienced with different databases would have to say about this.

this is the query out put
Attachment 97485
i need to eliminate duplicate names in datatable or in the query & the out must be
Attachment 97487

Can't be done, shouldn't be done. Unless you're prepared to transfer to a listview and use that column as the group property on each item.

At the DataTable level, I would look at DataTable.Merge method to eliminate dups.
Or perhaps use the following DataGridView to group by column

Code:

---

Public Class GroupByGrid
    Inherits DataGridView

    Protected Overrides Sub OnCellFormatting(ByVal args As DataGridViewCellFormattingEventArgs)
        MyBase.OnCellFormatting(args)

        ' First row always displays
        If args.RowIndex = 0 Then
            Return
        End If

        If IsRepeatedCellValue(args.RowIndex, args.ColumnIndex) Then
            args.Value = String.Empty
            args.FormattingApplied = True
        End If
    End Sub
    Private Function IsRepeatedCellValue(ByVal rowIndex As Integer, ByVal colIndex As Integer) As Boolean
        Dim currCell As DataGridViewCell = Rows(rowIndex).Cells(colIndex)
        Dim prevCell As DataGridViewCell = Rows(rowIndex - 1).Cells(colIndex)

        If (currCell.Value Is prevCell.Value) OrElse (currCell.Value IsNot Nothing AndAlso prevCell.Value IsNot Nothing AndAlso currCell.Value.ToString() = prevCell.Value.ToString()) Then
            Return True
        Else
            Return False
        End If

    End Function
    Protected Overrides Sub OnCellPainting(ByVal args As DataGridViewCellPaintingEventArgs)

        MyBase.OnCellPainting(args)

        args.AdvancedBorderStyle.Bottom = DataGridViewAdvancedCellBorderStyle.None

        ' Ignore column and row headers and first row
        If args.RowIndex < 1 OrElse args.ColumnIndex < 0 Then
            Return
        End If

        If IsRepeatedCellValue(args.RowIndex, args.ColumnIndex) Then
            args.AdvancedBorderStyle.Top = DataGridViewAdvancedCellBorderStyle.None
        Else
            args.AdvancedBorderStyle.Top = AdvancedCellBorderStyle.Top
        End If

    End Sub
End Class

---

kevin :wave: after long time i am getting you
i need to do it in datatable only,
a kind of looping + comparing prev row with next row + editing the datatble columns, it works but time consuming

is the LINQ can simplify this task ?

I would had thought the DataGridView I suggested would had done the job
Attachment 97527