try
{

String sConnString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=..\..\database\jason.mdb";

oledbConnection1 = new System.Data.OleDb.OleDbConnection(sConnString);
String sss = comboBox1.Text;

OleDbCommand oledbcmd = new OleDbCommand(" " +
" SELECT * From student,semester,achievement WHERE student.student_id = semester.student_id=@ id " +
" and semester.student_achievement = achievement.student_achievement ", oledbConnection1);

oledbcmd.Parameters.AddWithValue("@ id", comboBox1.Text);
OleDbDataReader sdr;
oledbConnection1.Open();
sdr = oledbcmd.ExecuteReader();
}
catch (OleDbException ex)
{
MessageBox.Show(ex.Message);
}