C# 连接MySQL数据库

string sql = "server=127.0.0.1;database=ramanager;uid=root;pwd=root";
            MySql.Data.MySqlClient.MySqlConnection conn = new MySql.Data.MySqlClient.MySqlConnection(sql);
            conn.Open();
            MySql.Data.MySqlClient.MySqlCommand comm = new MySql.Data.MySqlClient.MySqlCommand();
            comm.Connection = conn;
            comm.CommandText = "select count(*) from s_cert where username='" + USERNAME + "' and time='" + day + "' and caozuo='申请并下载'";
            //comm1.CommandText = "select count(*) from s_cert where username='" + USERNAME + "' and time='" + day + "' and caozuo='更新并下载'";
            string num = comm.ExecuteScalar().ToString();
            conn.Close();

            label28.Text = num;