VB中我已经对数据库中表数据的删除数据库中却还有数据，求大神帮忙，新手一个

[zhuxiansuola]

 private void button1_Click(object sender, EventArgs e)
        {
            if (textBox1.Text == "" || comboBox1.Text == "")
                MessageBox.Show("提示：请输入！", "警告");
            else
            {
                if (this.comboBox1.Text == "学号")
                {
                    string str = @"Data Source=lenovo-pc\sqlexpress;Initial catalog=用户;integrated Security=True";
                    SqlConnection conn = new SqlConnection(str);
                    conn.Open();
                    string sql = "Delete  from 成绩信息 where  学号 = '" + textBox1.Text + "'";
                    SqlCommand cmd = new SqlCommand(sql, conn);
                    conn.Close();
                }
            }
        }

[赵4老师]

权限问题。我猜。