The DataSet contains copy of the data we requested through the SQL statement. The SqlDataAdapter object allows us to populate DataTable in a DataSet. We can use Fill method in the SqlDataAdapter for populating data in a Dataset. We can populate Dataset with more than one table at a time using SqlDataAdapter Object. The DataTableCollection contains zero or more DataTable objects.
In some situation we want to combine the result of multiple SQL query as a single result set. In that case we can use the Dataset's Merge method for doing this. The tables involved in the merge should be identical, that is the columns are similar data types .
Private Sub GetUsersList()
Dim connetionString As String
Dim connection As SqlConnection
Dim command As SqlCommand
Dim adapter As New SqlDataAdapter
Dim ds As New DataSet
Dim dt As DataTable
Dim firstSql As String
Dim secondSql As String
Dim i As Integer
connetionString = "Data Source=.;Initial Catalog=Nafex;User ID=sa;Password=111"
firstSql = "Select * from tblUser"
secondSql = "Select * from tluVrType"
connection = New SqlConnection(connetionString)
command = New SqlCommand(firstSql, connection)
adapter.SelectCommand = command
adapter.SelectCommand.CommandText = secondSql
dt = ds.Tables(0)
For i = 0 To dt.Rows.Count - 1
MsgBox(dt.Rows(i).Item(0) & " -- " & dt.Rows(i).Item(1))
Catch ex As Exception
MsgBox("Can not open connection ! ")