使用mysql数据库
string connectionString = "server=127.0.0.1;database=rwdb;uid=root;pwd=123;charset=utf8;Allow User Variables=True;";
mysql = new MySqlConnection("server=127.0.0.1;database=rwdb;uid=root;pwd=123;charset=utf8");
mysql.QueryAsync<A>("select * from a");
mysql.ExecuteAsync($"delete from A where data<'{
DateTime.Now.AddDays(-saveDay).ToString("yyyy-MM-dd HH:mm:ss")}'");