MySQL中的不同圓角結果

Question

我有一個緯度\經度點數據庫。我正在嘗試按距離排序的DISTINCT四捨五入結果。我的查詢如下：

SELECT 
    DISTINCT ROUND(`lat`,2), ROUND(`lon`,2), 
    (3959 * acos(cos(radians(LAT_HERE)) 
      * cos(radians(`lat`)) 
      * cos(radians(`lon`) - radians(LONG_HERE)) 
      + sin(radians(LAT_HERE)) 
      * sin(radians(`lat`)))) AS distance 
FROM `user_data` 
HAVING distance <= 99 
ORDER BY distance 
LIMIT 100 

獨特的是在一輪之前運行。例如（29.333,29.334），（29.331,29.332）將顯示兩次。

Answer 1

嘗試使用GROUP BY

SELECT ROUND(`lat`,2), ROUND(`lon`,2), 
        (3959 * acos(cos(radians(LAT_HERE)) 
        * cos(radians(`lat`)) 
        * cos(radians(`lon`) - radians(LONG_HERE)) 
        + sin(radians(LAT_HERE)) 
        * sin(radians(`lat`)))) AS distance 
       FROM `user_data` 
       GROUP BY ROUND(`lat`,2) 
       HAVING distance <= 99 
       ORDER BY distance 
       LIMIT 100 

Answer 2

其實你是不正確的。 DISTINCT在先前評估的結果上運行。例如 運行：

select distinct round(a,2), round(b,2) 
from ((select 29.333 as a,29.334 as b) union (select 29.331,29.332)) t3; 

結果是：

+------------+------------+ 
| round(a,2) | round(b,2) | 
+------------+------------+ 
|  29.33 |  29.33 | 
+------------+------------+