错误：MySQL - 操作数应该包含1列。

Question

这个查询在我直接在MySQL中输入时可以工作，但在C#中却不行。

double deltaTime = (DateTime.Now - collectTime).TotalSeconds;


string query = String.Format("UPDATE buildings LEFT JOIN server_buildings ON buildings.global_id = server_buildings.global_id AND buildings.level = server_buildings.level SET buildings.storage = buildings.storage + (server_buildings.speed * {0} * IF(buildings.boost >= NOW(), 2, 1)) WHERE buildings.global_id IN('generator', 'test')", deltaTime / 3600d);

只是得到了错误MySQL - 操作数应该包含1列。感谢建议！ :)

预计随着时间的推移，它会在"storage"中增加值。

Answer 1

我对MySQL还比较新。这是带有参数的查询。

string query = String.Format("UPDATE buildings JOIN server_buildings ON buildings.global_id = server_buildings.global_id AND buildings.level = server_buildings.level SET buildings.storage = buildings.storage + (server_buildings.speed * ?Num * IF(buildings.boost >= NOW(), 2, 1)) WHERE buildings.global_id IN('generator', 'test')");
                     
            using (MySqlCommand command = new MySqlCommand(query, connection))
            {
                MySqlParameter param = new MySqlParameter("?Num", (deltaTime / 3600d));
                command.Parameters.Add(param);
      
               command.ExecuteNonQuery();
            }