Update Query not working

I have the following code :

function update_comp_count($lead_id, $sp_value, $field_number) {
    global $wpdb;

    $lead_detail_table = RGFormsModel::get_lead_details_table_name();

    $sql = $wpdb->prepare(" UPDATE $lead_detail_table SET value = %d WHERE lead_id = %d AND field_number = %d)", $sp_value, $lead_id, $field_number);

    $wpdb->query($sql);

}

I use similiar code for Inserting data into the database :

$lead_detail_table = RGFormsModel::get_lead_details_table_name();

	for ($i = 0; $i <= 6; $i++) {
		$sql = $wpdb->prepare(" INSERT INTO $lead_detail_table (lead_id, form_id, field_number, value)
								VALUES (%d, 7, %s, %s
								)", $lead_id, $new_stud_values[$i]->field, $new_stud_values[$i]->value);
		$wpdb->query($sql);
	}

The insert code works perfectly but the Update code doesn’t work at all. Any ideas on this?