How can I prevent inserting duplicate data into a SQL Server table?

Question

I have a series of data that need to be written into SQL, what should I do to check the data in SQL to prevent same data inserted into table?

Example data to be inse

Answer 1

Try This Easy way

  { 
        DataSet ds = New DataSet();
SqlConnection myCnn = New SqlConnection(cnn);
myCnn.Open();
                    SqlCommand _Query = New SqlCommand("Select *FROM CamNo1 where platename='" + Console.ReadLine + "' ", myCnn);
                  SqlDataAdapter  sda = New SqlDataAdapter(_Query);
                    sda.Fill(ds);

                    Int i = ds.Tables[0].Rows.Count;
                    If (i > 0) Then
                                {
                        MessageBox.Show("platename" + Console.WriteLine + "Already Exists ");
                        ds.Clear();
                    }
                    Else
                    {
                        SqlConnection myCnn = New SqlConnection(cnn);
String _state = "Insert into CamNo1(platename, date, camID, path, filename) OUTPUT INSERTED.platename values(@msg, getdate(), @camID, @path, @filename)";
SqlCommand _Query = New SqlCommand(_state, myCnn);

_Query.Parameters.AddWithValue("@msg", msg);
_Query.Parameters.AddWithValue("@camID", camID);
_Query.Parameters.AddWithValue("@path", i`enter code here`mageFile`);
_Query.Parameters.AddWithValue("@filename", Name);

Try
{
   myCnn.Open();
   String checkname = (String)_Query.ExecuteScalar();
   myCnn.Close();

   getcheckname = checkname;
   Console.WriteLine("OK");
}
Catch (Exception)
{
}
                    }

  }