从在线托管的mysql数据库中检索数据的最快方法是什么？

Question

I'm currently building an android app that stores data on a remote database, and I want to retrieve the data to the app, but this takes a while. So I want to know the best way to send data of retrieving the data to Android(Would Sqlite increase the performance of the app?).

Answer 1

You call the method GetDataFromDB(string query) very often. This is bad because you create a new SqlConnection and SqlCommand each time. This takes time and resources. Also, if there is any network delay, that is multiplied by the number of calls you are making. So it's just a bad idea.

I suggest that you call that method once and have it populate a collection like a Dictionary so that you can quickly look up your Username value from the user id key.

Like this:

// In the DataField class, have this code.
// This method will query the database for all usernames and user ids and
// return a Dictionary<int, string> where the key is the Id and the value is the 
// username. Make this a global variable within the DataField class.
Dictionary<int, string> usernameDict = GetDataFromDB("select id, username from Users");

// Then in the GetValue(int userId) method, do this:
public string GetValue(int userId)
{
    // Add some error handling and whatnot. 
    // And a better name for this method is GetUsername(int userId)
    return this.usernameDict[userId];
}

Suggestion 2 Here is another way that you can improve things, though slightly in this case—use the StringBuilder class. There are significant performance gains (here is an overview: http://support.microsoft.com/kb/306822 ).

SringBuilder sb = new StringBuilder();
sb.Append("<table><tr><th>Username</th>");
foreach (DataField f in fields)
{
    sb.Append("<th>" + f.Name + "</th>");
}

// Then, when you need the string
string html = sb.ToString();