Identical datatable 2 columns merging and summing one column in vb.net - vb.net

Question

I have 5 datatables which having each 3 columns (ID, Brand, Quanitiy) to derive the opening, purchase, sales and closing stock. The First 3 datatables should be merged and sum up to derive the opening stock as on given period. 4 th datatable is for Purchases done for the given period. The last one Datatable is for Sales done for the given period.
Here is my question:
How can i merge the 3 datatables and using the first 2 columns and summing the values?
How can i use the tables in crystal reports?
My code is :
Dim con As New ClassConnection
If con.Conn.State = ConnectionState.Closed Then con.Conn.Open()
'To get Opening Stock in Full Quantity
Dim sql As String = "SELECT tblBrand.B_ID AS ID, tblBrand.B_Name AS Brand," & _
" Sum (tblOp_Details.Net_Qty) AS Quantity FROM tblOp_Stock INNER JOIN (tblBrand INNER JOIN" & _
" tblOp_Details ON tblBrand.B_ID = tblOp_Details.B_ID) ON tblOp_Stock.Stk_ID = tblOp_Details.Stk_ID" & _
" WHERE tblOp_Stock.God_ID = #GID GROUP BY tblBrand.B_ID, tblBrand.B_Name"
'To get Purchases < start date and adding to the opening stock
Dim sql1 As String = "SELECT tblBrand.B_ID AS ID, tblBrand.B_Name AS Brand," & _
" Sum (tblPur_Details.Net_Qty) AS Quantity FROM tblPurchase INNER JOIN (tblBrand INNER JOIN" & _
" tblPur_Details ON tblBrand.B_ID = tblPur_Details.B_ID) ON tblPurchase.Pur_ID = tblPur_Details.Pur_ID" & _
" WHERE tblPurchase.God_ID = #GID AND tblPurchase.Rec_Date < #SDate GROUP BY tblBrand.B_ID, tblBrand.B_Name"
'To get Sales < Start date and subtracting to the above
Dim sql2 As String = "SELECT tblBrand.B_ID AS ID, tblBrand.B_Name AS Brand," & _
" Sum (tblSales_Details.Net_Qty) AS Quantity FROM tblSales INNER JOIN (tblBrand INNER JOIN" & _
" tblSales_Details ON tblBrand.B_ID = tblSales_Details.B_ID) ON tblSales.Sale_ID = tblSales_Details.Sale_ID" & _
" WHERE tblSales.God_ID = #GID AND tblSales.Sale_Date < #SDate GROUP BY tblBrand.B_ID, tblBrand.B_Name"
'The above 3 condition is for deriving opening stock as on given date
'To get Purchases >= Start Date and <= Start Date
Dim sql3 As String = "SELECT tblBrand.B_ID AS ID, tblBrand.B_Name AS Brand," & _
" Sum(tblPur_Details.Net_Qty) AS Quantity FROM tblBrand INNER JOIN (tblPurchase INNER JOIN" & _
" tblPur_Details ON tblPurchase.Pur_ID = tblPur_Details.Pur_ID) ON tblBrand.B_ID = tblPur_Details.B_ID" & _
" WHERE tblPurchase.God_ID = #GID And tblPurchase.Rec_Date >= #SDate And tblPurchase.Rec_Date" & _
" <= #EDate GROUP BY tblBrand.B_ID, tblBrand.B_Name"
'The above condition is for deriving Purchases as on given date
'To get Sales >= Start Date and <= Start Date
Dim sql4 As String = "SELECT tblBrand.B_ID AS ID, tblBrand.B_Name AS Brand," & _
" Sum(tblSales_Details.Net_Qty) AS Quantity FROM tblBrand INNER JOIN (tblSales INNER JOIN" & _
" tblSales_Details ON tblSales.Sale_ID = tblSales_Details.Sale_ID) ON tblBrand.B_ID = tblSales_Details.B_ID" & _
" WHERE tblSales.God_ID = #GID And tblSales.Sale_Date >= #SDate And tblSales.Sale_Date <= #EDate" & _
" And tblSales_Details.S_Active = #SAct GROUP BY tblBrand.B_ID, tblBrand.B_Name"
'The above condition is for deriving Sales as on given date
Dim da As New OleDb.OleDbDataAdapter(sql, con.Conn)
Dim da1 As New OleDb.OleDbDataAdapter(sql1, con.Conn)
Dim da2 As New OleDb.OleDbDataAdapter(sql2, con.Conn)
Dim da3 As New OleDb.OleDbDataAdapter(sql3, con.Conn)
Dim da4 As New OleDb.OleDbDataAdapter(sql4, con.Conn)
da.SelectCommand.Parameters.AddWithValue("#GID", Me.stBar_G_ID.Text)
da1.SelectCommand.Parameters.AddWithValue("#GID", Me.stBar_G_ID.Text)
da1.SelectCommand.Parameters.AddWithValue("#SDate", Me.dtpStart.ToString)
da2.SelectCommand.Parameters.AddWithValue("#GID", Me.stBar_G_ID.Text)
da2.SelectCommand.Parameters.AddWithValue("#SDate", Me.dtpStart.ToString)
da3.SelectCommand.Parameters.AddWithValue("#GID", Me.stBar_G_ID.Text)
da3.SelectCommand.Parameters.AddWithValue("#SDate", Me.dtpStart.ToString)
da3.SelectCommand.Parameters.AddWithValue("#EDate", Me.dtpEnd.ToString)
da4.SelectCommand.Parameters.AddWithValue("#GID", Me.stBar_G_ID.Text)
da4.SelectCommand.Parameters.AddWithValue("#SDate", Me.dtpStart.ToString)
da4.SelectCommand.Parameters.AddWithValue("#EDate", Me.dtpEnd.ToString)
da4.SelectCommand.Parameters.AddWithValue("#SAct", "Yes")
Dim dt As New DataTable
Dim dt1 As New DataTable
Dim dt2 As New DataTable
Dim dt3 As New DataTable
Dim dt4 As New DataTable

Answer 1

Ignoring the fact that such operations should be done in the database instead of memory, you can use Linq-To-DataSet which is a subset of Linq-To-Objects.
If you want to concatenate the three tables, group by ID + Brand to get the sum of Quantity:
Dim allRows = dt1.AsEnumerable().Concat(dt2.AsEnumerable()).Concat(dt3.AsEnumerable())
Dim query = From row In allRows
Let GroupColumns = New With {
.Id = row.Field(Of Int32)("Id"),
.Brand = row.Field(Of String)("Brand")
}
Group row By GroupColumns Into Group
Select New With {
.Id = GroupColumns.Id,
.Brand = GroupColumns.Brand,
.SumQuantity = Group.Sum(Function(row) row.Field(Of Int32)("Quantity"))
}
Fill the merged table from the query:
Dim dt As DataTable = dt1.Clone() ' empty, same columns
For Each x In query
Dim row = dt.Rows.Add()
row.SetField("Id", x.Id)
row.SetField("Brand", x.Brand)
row.SetField("Quantity", x.SumQuantity)
Next