Get min, max and avg records from a database using SQL

con.Open();

str = "select * from student";

com = new OleDbCommand(str, con);

oledbda = new OleDbDataAdapter(com);

ds = new DataSet();

oledbda.Fill(ds, "student");

dataGridView1.DataSource = ds;

dataGridView1.DataMember = "student";

con.Close();

}

private void button1_Click(object sender, EventArgs e)

{

OleDbConnection con = new OleDbConnection(ConnectionString);

con.Open();

str = "select max(smarks)from student";

com = new OleDbCommand(str, con);

textBox1.Text = com.ExecuteScalar().ToString();

con.Close();

}

private void button2_Click(object sender, EventArgs e)

{

OleDbConnection con = new OleDbConnection(ConnectionString);

con.Open();

str = "select min(smarks)from student";

com = new OleDbCommand(str, con);

textBox2.Text = com.ExecuteScalar().ToString();

con.Close();

}

private void button3_Click(object sender, EventArgs e)

{

OleDbConnection con = new OleDbConnection(ConnectionString);

con.Open();

str = "select avg(smarks)from student";

com = new OleDbCommand(str, con);

textBox3.Text = com.ExecuteScalar().ToString();

con.Close();

}

}

}