WHERE條款中的多個OR條件

Question

我處於需要收集某個100m方形距離內的某些緯度數據點的數據的情況。我目前正在運行一個查詢如下，這適用於較少的位置。下面的15個數據點的查詢需要大約10分鐘的時間才能運行，但這種方法不能用更多的數據點進行擴展。我運行了一個具有4000個緯度數據點（與美國地圖上的4000個位置相關）的類似查詢，並且查詢需要30個小時才能運行。我知道哪個語句按行逐行掃描整個表，這就是爲什麼查詢運行得真的很長。即使我選擇較少的所需列，查詢也需要很長時間才能運行。你們有沒有更好的方法來完成這一點。請指教。

  create table crt1 
as 
select * from masterdata 
where 
(round(device_lat,4) >= 33.7306 and round(device_lat , 4) <= 33.7316 and round(device_lon,4) >= -117.8364 and round(device_lon , 4) <= -117.8354) or 

(round(device_lat,4) >= 37.927 and round(device_lat , 4) <= 37.928 and round(device_lon,4) >= -122.517 and round(device_lon , 4) <= -122.516) or 

(round(device_lat,4) >= 30.2711 and round(device_lat , 4) <= 30.2721 and round(device_lon,4) >= -97.7544 and round(device_lon , 4) <= -97.7534) or 

(round(device_lat,4) >= 33.0673 and round(device_lat , 4) <= 33.0683 and round(device_lon,4) >= -117.2642 and round(device_lon , 4) <= -117.2632) or 

(round(device_lat,4) >= 34.8271 and round(device_lat , 4) <= 34.8281 and round(device_lon,4) >= -82.3011 and round(device_lon , 4) <= -82.3001) or 

(round(device_lat,4) >= 32.9258 and round(device_lat , 4) <= 32.9268 and round(device_lon,4) >= -96.8311 and round(device_lon , 4) <= -96.8301) or 

(round(device_lat,4) >= 45.0917 and round(device_lat , 4) <= 45.0927 and round(device_lon,4) >= -93.4272 and round(device_lon , 4) <= -93.4262) or 

(round(device_lat,4) >= 36.0214 and round(device_lat , 4) <= 36.0224 and round(device_lon,4) >= -115.0853 and round(device_lon , 4) <= -115.0843) or 

(round(device_lat,4) >= 47.2156 and round(device_lat , 4) <= 47.2166 and round(device_lon,4) >= -122.2351 and round(device_lon , 4) <= -122.2341) or 

(round(device_lat,4) >= 32.2492 and round(device_lat , 4) <= 32.2502 and round(device_lon,4) >= -110.8845 and round(device_lon , 4) <= -110.8835) or 

(round(device_lat,4) >= 32.286 and round(device_lat , 4) <= 32.287 and round(device_lon,4) >= -110.9753 and round(device_lon , 4) <= -110.9743) or 

(round(device_lat,4) >= 36.8477 and round(device_lat , 4) <= 36.8487 and round(device_lon,4) >= -119.7911 and round(device_lon , 4) <= -119.7901) or 

(round(device_lat,4) >= 36.0842 and round(device_lat , 4) <= 36.0852 and round(device_lon,4) >= -79.8363 and round(device_lon , 4) <= -79.8353) or 

(round(device_lat,4) >= 39.0612 and round(device_lat , 4) <= 39.0622 and round(device_lon,4) >= -77.1245 and round(device_lon , 4) <= -77.1235) or 

(round(device_lat,4) >= 32.8389 and round(device_lat , 4) <= 32.8399 and round(device_lon,4) >= -117.1629 and round(device_lon , 4) <= -117.1619) or 

(round(device_lat,4) >= 61.1948 and round(device_lat , 4) <= 61.1958 and round(device_lon,4) >= -149.9061 and round(device_lon , 4) <= -149.9051); 

Answer 1

爲本：masterdata(device_lon)

其次創建masterdata(device_lat)，還有一個是指數，重鑄這個查詢的每一行：

(device_lat >= 32.8389 and device_lat <= 32.8399 and 
device_lon >= -117.1629 and device_lon <= -117.1619) or ... 

您使用的round(lat,4)擊敗了您的使用索引能力對於搜索來說，這確實很慢：它必須多次掃描你的表格。

如果您碰巧正在處理GPS數據，或者您碰巧正在使用球形地球近似來計算距離，那麼round()函數在精確度上就沒有任何好處。全球位置的實際精度約爲小數點後四位，精度的更多數字既不會幫助也不會損害您的準確性。

如果你理解通用橫軸墨卡託投影或者蘭伯特投影這兩個術語，那麼你實際上對你的數據的精確度比你的問題指出的要多得多，你應該使用這些知識。

其實，說實話，你應該改寫這個像這樣：

SELECT m.* 
    FROM masterdata AS m 
    JOIN (
     SELECT radius AS 0.0005 
     ) AS radius 
    JOIN ( /* make a virtual table of your bunch of centerpoints */ 
     SELECT 33.7311 AS lat, -117.8359 AS long 
     UNION ALL 
     SELECT 37.9275, -122.5165 
     UNION ALL 
     SELECT somelat, somelon 
     UNION ALL ... 
    ) AS points 
    ON m.device_lat >= points.lat - radius 
    AND m.device_lat <= points.lat + radius 
    AND m.device_long >= points.long - (radius/COS(RADIANS(points.lat))) 
    AND m.device_long <= points.long + (radius/COS(RADIANS(points.lat))) 

這將盡可能高效地讓你一個不錯的結果。它會調整您的經度搜索值radius以糾正經度線距離赤道較近的事實。它可以讓MySQL優化。

編輯

我只注意到貴100平方米的要求，我將解釋爲+/- 50 M於地面的邊界框。 （這裏您接近精度限制。）

緯度爲111045米，所以您需要的半徑值（50.0/111045.0）恰好約爲0.0004503。您在問題中顯示的價值0.0005更像是111平方米。

這是一些背景。 http://www.plumislandmedia.net/mysql/haversine-mysql-nearest-loc/