特定半径内的邮编

Question

我正在查找SQL查询以让我检索特定半径内的ZipCodes。

我有一个名为tblZip的表，其列为：Zipcode,Lat（纬度），Long（经度）。

tblZip 

Zipcode | Lat | Long 
Short Text | Number | Number 

我已经检查了一些其他的答案是建议使用Great-circle Distance但我似乎不明白它是如何工作的。我只是看到所有的转换成弧度和度数而头痛，我真的很想理解它，但是我对数学很不好。

我感谢您的帮助和指导。

PS：我正在使用Microsoft Access数据库。

Answer 1

考虑在VBA函数中使用半正向公式（借用here）。然后让它在你的SQL查询中调用。甚至可以按照您的需求通​​过WHERE条款按距离过滤您的查询。请注意：此解决方案仅适用于MSAccess.exe程序。您将无法通过ODBC/OLEDB从外部调用它。

而且由于您需要比较地理编码，因此下面的SQL查询使用交叉连接，其中每个记录都与表中的每个其他记录进行比较。另外，查询避免了反向重复和相同匹配的配对，从而减小了大小。但是，如果表格很大，因为交叉连接对自我返回N 记录，即在重复过滤之前。

SQL

SELECT z1.Zipcode, z2.Zipcode, 
     GetDistance(z1.Lat, z1.Lon, z2.Lat, z2.Lon) As km_distance 
FROM tblZip z1, tblZip z2 
WHERE z1.Zipcode > z2.Zipcode 
AND GetDistance(s1.lat, s1.lon, s1.lat, s2.lon) <= 5; 

VBA（具有5 km或更小距离邮政编码配对）（独立模块中保存）

Function GetDistance(lat1Degrees As Double, lon1Degrees As Double, lat2Degrees As Double, lon2Degrees As Double) As Double 

    Dim earthSphereRadiusKilometers As Double 
    Dim kilometerConversionToMilesFactor As Double 
    Dim lat1Radians As Double 
    Dim lon1Radians As Double 
    Dim lat2Radians As Double 
    Dim lon2Radians As Double 
    Dim AsinBase As Double 
    Dim DerivedAsin As Double 

    'Mean radius of the earth (replace with 3443.89849 to get nautical miles) 
    earthSphereRadiusKilometers = 6371 

    'Convert kilometers into miles (replace 0.621371 with 1 to keep in kilometers) 
    kilometerConversionToMilesFactor = 0.621371 

    'Convert each decimal degree to radians 
    lat1Radians = (lat1Degrees/180) * (4 * ATN(1)) 
    lon1Radians = (lon1Degrees/180) * (4 * ATN(1)) 
    lat2Radians = (lat2Degrees/180) * (4 * ATN(1)) 
    lon2Radians = (lon2Degrees/180) * (4 * ATN(1)) 

    AsinBase = Sin(Sqr(Sin((lat1Radians - lat2Radians)/2)^2 + Cos(lat1Radians) * Cos(lat2Radians) * Sin((lon1Radians - lon2Radians)/2)^2)) 
    DerivedAsin = (AsinBase/Sqr(-AsinBase * AsinBase + 1)) 

    'Get distance from [lat1,lon1] to [lat2,lon2] 
    GetMiles = Round(2 * DerivedAsin * (earthSphereRadiusKilometers * kilometerConversionToMilesFactor), 2) 

End Function