c# - 使用参数比较数据库中的日期

Question

string queryString = "SELECT SUM(skupaj_kalorij)as Skupaj_Kalorij  "
                + "FROM (obroki_save LEFT JOIN users ON obroki_save.ID_uporabnika=users.ID)"
                + "WHERE (users.ID= " + a.ToString() + ") AND (obroki_save.datum= @datum)";

            using (OleDbCommand cmd = new OleDbCommand(queryString,database))                                    
                {
                    DateTime datum = DateTime.Today;
                    cmd.Parameters.AddWithValue("@datum", datum);
                }
            loadDataGrid2(queryString);

我现在尝试使用参数。但我真的不知道如何正确地做到这一点。我尝试这样做，但参数数据没有获得任何值(根据c#)。

Answer 1

请尝试这个:

database = new OleDbConnection(connectionString);
                database.Open();
                date = DateTime.Now.ToShortDateString();
                string queryString = "SELECT SUM(skupaj_kalorij)as Skupaj_Kalorij  "
                    + "FROM (obroki_save LEFT JOIN users ON obroki_save.ID_uporabnika=users.ID)" 
                    + "WHERE users.ID= " + a.ToString()+" AND obroki_save.datum= '" +DateTime.Today.ToShortDateString() + "'";
                loadDataGrid2(queryString);

与Date一起使用时，必须这样写

select * from table where date = '@date'

不喜欢

select * from table where date = @date