使用SQLITE的Long Lat coord之间的距离 [英] Distance between Long Lat coord using SQLITE

问题描述

我有一个带有长商店的sqlite数据库，我想找出最近的5家商店。

I've got an sqlite db with long and lat of shops and I want to find out the closest 5 shops.

所以下面的代码工作正常。

So the following code works fine.

    if(sqlite3_prepare_v2(db, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK) {


    while (sqlite3_step(compiledStatement) == SQLITE_ROW) {

        NSString *branchStr = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 0)];
        NSNumber *fLat = [NSNumber numberWithFloat:(float)sqlite3_column_double(compiledStatement, 1)];
        NSNumber *fLong = [NSNumber numberWithFloat:(float)sqlite3_column_double(compiledStatement, 2)];

        NSLog(@"Address %@, Lat = %@, Long = %@", branchStr, fLat, fLong);
        CLLocation *location1 = [[CLLocation alloc] initWithLatitude:currentLocation.coordinate.latitude longitude:currentLocation.coordinate.longitude];
        CLLocation *location2 = [[CLLocation alloc] initWithLatitude:[fLat floatValue] longitude:[fLong floatValue]];

        NSLog(@"Distance i meters: %f", [location1 getDistanceFrom:location2]);
        [location1 release];
        [location2 release];
    }       
}

我知道我到每个商店的距离。我的问题是。

I know the distance from where I am to each shop. My question is.

1. 将距离放回sqlite行是否更好，当我逐步通过时，我有一行数据库。我怎么做？我是否使用UPDATE语句？有人有一段代码可以帮助我。

1. Is it better to put the distance back into the sqlite row, I have the row when I step thru the database. How do I do that? Do I use the UPDATE statement? Does someone have a piece of code to help me.

我可以将sqlite读入一个数组，然后对数组进行排序。你是否推荐上述方法？这样效率更高吗？

I can read the sqlite into an array and then sort the array. Do you recommend this over the above approach? Is this more efficient?

最后，如果有人有更好的方法来获得最近的5家商店，那就爱听它。

Finally, if someone has a better way to get the closest 5 shops, love to hear it.

推荐答案

在SQL中查找附近位置的最快方法是在SQL查询中使用Haversine公式。谷歌搜索sqlite和Haversine，你会发现一个实现。

The fastest way to find nearby locations in SQL is to use the Haversine formula in an SQL query. Do a Google search for sqlite and Haversine and you'll find an implementation.

这是我以前用过的一个：

Here's one I've used before:

http://www.thismuchiknow.co.uk/?p=71

这篇关于使用SQLITE的Long Lat coord之间的距离的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！